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# Dependency Management
- [Dependency Management](#dependency-management)
- [Instancing methods](#instancing-methods)
- [Get.put()](#getput)
- [Get.lazyPut](#getlazyput)
- [Get.putAsync](#getputasync)
- [Get.create](#getcreate)
- [Using instantiated methods/classes](#using-instantiated-methodsclasses)
- [Specifying an alternate instance](#specifying-an-alternate-instance)
- [Differences between methods](#differences-between-methods)
- [Bindings](#bindings)
- [Bindings class](#bindings-class)
- [BindingsBuilder](#bindingsbuilder)
- [SmartManagement](#smartmanagement)
- [How to change](#how-to-change)
- [SmartManagement.full](#smartmanagementfull)
- [SmartManagement.onlyBuilders](#smartmanagementonlybuilders)
- [SmartManagement.keepFactory](#smartmanagementkeepfactory)
- [How bindings work under the hood](#how-bindings-work-under-the-hood)
- [Notes](#notes)
Get has a simple and powerful dependency manager that allows you to retrieve the same class as your Bloc or Controller with just 1 lines of code, no Provider context, no inheritedWidget:
```dart
Controller controller = Get.put(Controller()); // Rather Controller controller = Controller();
```
Instead of instantiating your class within the class you are using, you are instantiating it within the Get instance, which will make it available throughout your App.
So you can use your controller (or Bloc class) normally
- Note: If you are using Get's State Manager, pay more attention to the [Bindings](#bindings) api, which will make easier to connect your view to your controller.
- Note²: Get dependency management is decloupled from other parts of the package, so if for example your app is already using a state manager (any one, it doesn't matter), you don't need to change that, you can use this dependency injection manager with no problems at all
## Instancing methods
The methods and it's configurable parameters are:
### Get.put()
The most common way of inserting a dependency. Good for the controllers of your views for example.
```dart
Get.put<SomeClass>(SomeClass());
Get.put<LoginController>(LoginController(), permanent: true);
Get.put<ListItemController>(ListItemController, tag: "some unique string");
```
This is all options you can set when using put:
```dart
Get.put<S>(
// mandatory: the class that you want to get to save, like a controller or anything
// note: "S" means that it can be a class of any type
S dependency
// optional: this is for when you want multiple classess that are of the same type
// since you normally get a class by using Get.find<Controller>(),
// you need to use tag to tell which instance you need
// must be unique string
String tag,
// optional: by default, get will dispose instances after they are not used anymore (example,
// the controller of a view that is closed), but you might need that the instance
// to be kept there throughout the entire app, like an instance of sharedPreferences or something
// so you use this
// defaults to false
bool permanent = false,
// optional: allows you after using an abstract class in a test, replace it with another one and follow the test.
// defaults to false
bool overrideAbstract = false,
// optional: allows you to create the dependency using function instead of the dependency itself.
// this one is not commonly used
InstanceBuilderCallback<S> builder,
)
```
### Get.lazyPut
It is possible to lazyLoad a dependency so that it will be instantiated only when is used. Very useful for computational expensive classes or if you want to instantiate several classes in just one place (like in a Bindings class) and you know you will not gonna use that class at that time.
```dart
/// ApiMock will only be called when someone uses Get.find<ApiMock> for the first time
Get.lazyPut<ApiMock>(() => ApiMock());
Get.lazyPut<FirebaseAuth>(
() {
// ... some logic if needed
return FirebaseAuth();
},
tag: Math.random().toString(),
fenix: true
)
Get.lazyPut<Controller>( () => Controller() )
```
This is all options you can set when using lazyPut:
```dart
Get.lazyPut<S>(
// mandatory: a method that will be executed when your class is called for the first time
InstanceBuilderCallback builder,
// optional: same as Get.put(), it is used for when you want multiple different instance of a same class
// must be unique
String tag,
// optional: It is similar to "permanent", the difference is that the instance is discarded when
// is not being used, but when it's use is needed again, Get will recreate the instance
// just the same as "SmartManagement.keepFactory" in the bindings api
// defaults to false
bool fenix = false
)
```
### Get.putAsync
If you want to register an asynchronous instance, you can use `Get.putAsync`:
```dart
Get.putAsync<SharedPreferences>(() async {
final prefs = await SharedPreferences.getInstance();
await prefs.setInt('counter', 12345);
return prefs;
});
Get.putAsync<YourAsyncClass>( () async => await YourAsyncClass() )
```
This is all options you can set when using putAsync:
```dart
Get.putAsync<S>(
// mandatory: an async method that will be executed to instantiate your class
AsyncInstanceBuilderCallback<S> builder,
// optional: same as Get.put(), it is used for when you want multiple different instance of a same class
// must be unique
String tag,
// optional: same as in Get.put(), used when you need to maintain that instance alive in the entire app
// defaults to false
bool permanent = false
)
```
### Get.create
This one is tricky. A detailed explanation of what this is and the differences between the other one can be found on [Differences between methods:](#differences-between-methods) section
```dart
Get.Create<SomeClass>(() => SomeClass());
Get.Create<LoginController>(() => LoginController());
```
This is all options you can set when using create:
```dart
Get.create<S>(
// required: a function that returns a class that will be "fabricated" every
// time `Get.find()` is called
// Example: Get.create<YourClass>(() => YourClass())
FcBuilderFunc<S> builder,
// optional: just like Get.put(), but it is used when you need multiple instances
// of a of a same class
// Useful in case you have a list that each item need it's own controller
// needs to be a unique string. Just change from tag to name
String name,
// optional: just like int`Get.put()`, it is for when you need to keep the
// instance alive thoughout the entire app. The difference is in Get.create
// permanent is true by default
bool permanent = true
```
## Using instantiated methods/classes
Imagine that you have navigated through numerous routes, and you need a data that was left behind in your controller, you would need a state manager combined with the Provider or Get_it, correct? Not with Get. You just need to ask Get to "find" for your controller, you don't need any additional dependencies:
```dart
final controller = Get.find<Controller>();
// OR
Controller controller = Get.find();
// Yes, it looks like Magic, Get will find your controller, and will deliver it to you.
// You can have 1 million controllers instantiated, Get will always give you the right controller.
```
And then you will be able to recover your controller data that was obtained back there:
```dart
Text(controller.textFromApi);
```
Since the returned value is a normal class, you can do anything you want:
```dart
int count = Get.find<SharedPreferences>().getInt('counter');
print(count); // out: 12345
```
To remove an instance of Get:
```dart
Get.delete<Controller>(); //usually you don't need to do this because GetX already delete unused controllers
```
## Specifying an alternate instance
A currently inserted instance can be replaced with a similar or extended class instance by using the `replace` or `lazyReplace` method. This can then be retrieved by using the original class.
```dart
abstract class BaseClass {}
class ParentClass extends BaseClass {}
class ChildClass extends ParentClass {
bool isChild = true;
}
Get.put<BaseClass>(ParentClass());
Get.replace<BaseClass>(ChildClass());
final instance = Get.find<BaseClass>();
print(instance is ChildClass); //true
class OtherClass extends BaseClass {}
Get.lazyReplace<BaseClass>(() => OtherClass());
final instance = Get.find<BaseClass>();
print(instance is ChildClass); // false
print(instance is OtherClass); //true
```
## Differences between methods
First, let's of the `fenix` of Get.lazyPut and the `permanent` of the other methods.
The fundamental difference between `permanent` and `fenix` is how you want to store your instances.
Reinforcing: by default, GetX deletes instances when they are not in use.
It means that: If screen 1 has controller 1 and screen 2 has controller 2 and you remove the first route from stack, (like if you use `Get.off()` or `Get.offNamed()`) the controller 1 lost its use so it will be erased.
But if you want to opt for using `permanent:true`, then the controller will not be lost in this transition - which is very useful for services that you want to keep alive throughout the entire application.
`fenix` in the other hand is for services that you don't worry in losing between screen changes, but when you need that service, you expect that it is alive. So basically, it will dispose the unused controller/service/class, but when you need it, it will "recreate from the ashes" a new instance.
Proceeding with the differences between methods:
- Get.put and Get.putAsync follows the same creation order, with the difference that the second uses an asynchronous method: those two methods creates and initializes the instance. That one is inserted directly in the memory, using the internal method `insert` with the parameters `permanent: false` and `isSingleton: true` (this isSingleton parameter only purpose is to tell if it is to use the dependency on `dependency` or if it is to use the dependency on `FcBuilderFunc`). After that, `Get.find()` is called that immediately initialize the instances that are on memory.
- Get.create: As the name implies, it will "create" your dependency! Similar to `Get.put()`, it also calls the internal method `insert` to instancing. But `permanent` became true and `isSingleton` became false (since we are "creating" our dependency, there is no way for it to be a singleton instace, that's why is false). And because it has `permanent: true`, we have by default the benefit of not losing it between screens! Also, `Get.find()` is not called immediately, it wait to be used in the screen to be called. It is created this way to make use of the parameter `permanent`, since then, worth noticing, `Get.create()` was made with the goal of create not shared instances, but don't get disposed, like for example a button in a listView, that you want a unique instance for that list - because of that, Get.create must be used together with GetWidget.
- Get.lazyPut: As the name implies, it is a lazy proccess. The instance is create, but it is not called to be used immediately, it remains waiting to be called. Contrary to the other methods, `insert` is not called here. Instead, the instance is inserted in another part of the memory, a part responsible to tell if the instance can be recreated or not, let's call it "factory". If we want to create something to be used later, it will not be mix with things been used right now. And here is where `fenix` magic enters: if you opt to leaving `fenix: false`, and your `smartManagement` are not `keepFactory`, then when using `Get.find` the instance will change the place in the memory from the "factory" to common instance memory area. Right after that, by default it is removed from the "factory". Now, if you opt for `fenix: true`, the instance continues to exist in this dedicated part, even going to the common area, to be called again in the future.
## Bindings
One of the great differentials of this package, perhaps, is the possibility of full integration of the routes, state manager and dependency manager.
When a route is removed from the Stack, all controllers, variables, and instances of objects related to it are removed from memory. If you are using streams or timers, they will be closed automatically, and you don't have to worry about any of that.
In version 2.10 Get completely implemented the Bindings API.
Now you no longer need to use the init method. You don't even have to type your controllers if you don't want to. You can start your controllers and services in the appropriate place for that.
The Binding class is a class that will decouple dependency injection, while "binding" routes to the state manager and dependency manager.
This allows Get to know which screen is being displayed when a particular controller is used and to know where and how to dispose of it.
In addition, the Binding class will allow you to have SmartManager configuration control. You can configure the dependencies to be arranged when removing a route from the stack, or when the widget that used it is laid out, or neither. You will have intelligent dependency management working for you, but even so, you can configure it as you wish.
### Bindings class
- Create a class and implements Binding
```dart
class HomeBinding implements Bindings {}
```
Your IDE will automatically ask you to override the "dependencies" method, and you just need to click on the lamp, override the method, and insert all the classes you are going to use on that route:
```dart
class HomeBinding implements Bindings {
@override
void dependencies() {
Get.lazyPut<HomeController>(() => HomeController());
Get.put<Service>(()=> Api());
}
}
class DetailsBinding implements Bindings {
@override
void dependencies() {
Get.lazyPut<DetailsController>(() => DetailsController());
}
}
```
Now you just need to inform your route, that you will use that binding to make the connection between route manager, dependencies and states.
- Using named routes:
```dart
getPages: [
GetPage(
name: '/',
page: () => HomeView(),
binding: HomeBinding(),
),
GetPage(
name: '/details',
page: () => DetailsView(),
binding: DetailsBinding(),
),
];
```
- Using normal routes:
```dart
Get.to(Home(), binding: HomeBinding());
Get.to(DetailsView(), binding: DetailsBinding())
```
There, you don't have to worry about memory management of your application anymore, Get will do it for you.
The Binding class is called when a route is called, you can create an "initialBinding in your GetMaterialApp to insert all the dependencies that will be created.
```dart
GetMaterialApp(
initialBinding: SampleBind(),
home: Home(),
);
```
### BindingsBuilder
The default way of creating a binding is by creating a class that implements Bindings.
But alternatively, you can use `BindingsBuilder` callback so that you can simply use a function to instantiate whatever you desire.
Example:
```dart
getPages: [
GetPage(
name: '/',
page: () => HomeView(),
binding: BindingsBuilder(() {
Get.lazyPut<ControllerX>(() => ControllerX());
Get.put<Service>(()=> Api());
}),
),
GetPage(
name: '/details',
page: () => DetailsView(),
binding: BindingsBuilder(() {
Get.lazyPut<DetailsController>(() => DetailsController());
}),
),
];
```
That way you can avoid to create one Binding class for each route making this even simpler.
Both ways of doing work perfectly fine and we want you to use what most suit your tastes.
### SmartManagement
GetX by default disposes unused controllers from memory, even if a failure occurs and a widget that uses it is not properly disposed.
This is what is called the `full` mode of dependency management.
But if you want to change the way GetX controls the disposal of classes, you have `SmartManagement` class that you can set different behaviors.
#### How to change
If you want to change this config (which you usually don't need) this is the way:
```dart
void main () {
runApp(
GetMaterialApp(
smartManagement: SmartManagement.onlyBuilders //here
home: Home(),
)
)
}
```
#### SmartManagement.full
It is the default one. Dispose classes that are not being used and were not set to be permanent. In the majority of the cases you will want to keep this config untouched. If you new to GetX then don't change this.
#### SmartManagement.onlyBuilders
With this option, only controllers started in `init:` or loaded into a Binding with `Get.lazyPut()` will be disposed.
If you use `Get.put()` or `Get.putAsync()` or any other approach, SmartManagement will not have permissions to exclude this dependency.
With the default behavior, even widgets instantiated with "Get.put" will be removed, unlike SmartManagement.onlyBuilders.
#### SmartManagement.keepFactory
Just like SmartManagement.full, it will remove it's dependencies when it's not being used anymore. However, it will keep their factory, which means it will recreate the dependency if you need that instance again.
### How bindings work under the hood
Bindings creates transitory factories, which are created the moment you click to go to another screen, and will be destroyed as soon as the screen-changing animation happens.
This happens so fast that the analyzer will not even be able to register it.
When you navigate to this screen again, a new temporary factory will be called, so this is preferable to using SmartManagement.keepFactory, but if you don't want to create Bindings, or want to keep all your dependencies on the same Binding, it will certainly help you.
Factories take up little memory, they don't hold instances, but a function with the "shape" of that class you want.
This has a very low cost in memory, but since the purpose of this lib is to get the maximum performance possible using the minimum resources, Get removes even the factories by default.
Use whichever is most convenient for you.
## Notes
- DO NOT USE SmartManagement.keepFactory if you are using multiple Bindings. It was designed to be used without Bindings, or with a single Binding linked in the GetMaterialApp's initialBinding.
- Using Bindings is completely optional, if you want you can use `Get.put()` and `Get.find()` on classes that use a given controller without any problem.
However, if you work with Services or any other abstraction, I recommend using Bindings for a better organization.
... ...
- [Route Management](#route-management)
- [How to use](#how-to-use)
- [Navigation without named routes](#navigation-without-named-routes)
- [Navigation with named routes](#navigation-with-named-routes)
- [Send data to named Routes](#send-data-to-named-routes)
- [Dynamic urls links](#dynamic-urls-links)
- [Middleware](#middleware)
- [Navigation without context](#navigation-without-context)
- [SnackBars](#snackbars)
- [Dialogs](#dialogs)
- [BottomSheets](#bottomsheets)
- [Nested Navigation](#nested-navigation)
# Route Management
This is the complete explanation of all there is to Getx when the matter is route management.
## How to use
Add this to your pubspec.yaml file:
```yaml
dependencies:
get:
```
If you are going to use routes/snackbars/dialogs/bottomsheets without context, or use the high-level Get APIs, you need to simply add "Get" before your MaterialApp, turning it into GetMaterialApp and enjoy!
```dart
GetMaterialApp( // Before: MaterialApp(
home: MyHome(),
)
```
## Navigation without named routes
To navigate to a new screen:
```dart
Get.to(NextScreen());
```
To close snackbars, dialogs, bottomsheets, or anything you would normally close with Navigator.pop(context);
```dart
Get.back();
```
To go to the next screen and no option to go back to the previous screen (for use in SplashScreens, login screens and etc.)
```dart
Get.off(NextScreen());
```
To go to the next screen and cancel all previous routes (useful in shopping carts, polls, and tests)
```dart
Get.offAll(NextScreen());
```
To navigate to the next route, and receive or update data as soon as you return from it:
```dart
var data = await Get.to(Payment());
```
on other screen, send a data for previous route:
```dart
Get.back(result: 'success');
```
And use it:
ex:
```dart
if(data == 'success') madeAnything();
```
Don't you want to learn our syntax?
Just change the Navigator (uppercase) to navigator (lowercase), and you will have all the functions of the standard navigation, without having to use context
Example:
```dart
// Default Flutter navigator
Navigator.of(context).push(
context,
MaterialPageRoute(
builder: (BuildContext context) {
return HomePage();
},
),
);
// Get using Flutter syntax without needing context
navigator.push(
MaterialPageRoute(
builder: (_) {
return HomePage();
},
),
);
// Get syntax (It is much better, but you have the right to disagree)
Get.to(HomePage());
```
## Navigation with named routes
- If you prefer to navigate by namedRoutes, Get also supports this.
To navigate to nextScreen
```dart
Get.toNamed("/NextScreen");
```
To navigate and remove the previous screen from the tree.
```dart
Get.offNamed("/NextScreen");
```
To navigate and remove all previous screens from the tree.
```dart
Get.offAllNamed("/NextScreen");
```
To define routes, use GetMaterialApp:
```dart
void main() {
runApp(
GetMaterialApp(
initialRoute: '/',
getPages: [
GetPage(name: '/', page: () => MyHomePage()),
GetPage(name: '/second', page: () => Second()),
GetPage(
name: '/third',
page: () => Third(),
transition: Transition.zoom
),
],
)
);
}
```
To handle navigation to non-defined routes (404 error), you can define an unknownRoute page in GetMaterialApp.
```dart
void main() {
runApp(
GetMaterialApp(
unknownRoute: GetPage(name: '/notfound', page: () => UnknownRoutePage()),
initialRoute: '/',
getPages: [
GetPage(name: '/', page: () => MyHomePage()),
GetPage(name: '/second', page: () => Second()),
],
)
);
}
```
### Send data to named Routes
Just send what you want for arguments. Get accepts anything here, whether it is a String, a Map, a List, or even a class instance.
```dart
Get.toNamed("/NextScreen", arguments: 'Get is the best');
```
on your class or controller:
```dart
print(Get.arguments);
//print out: Get is the best
```
### Dynamic urls links
Get offer advanced dynamic urls just like on the Web. Web developers have probably already wanted this feature on Flutter, and most likely have seen a package promise this feature and deliver a totally different syntax than a URL would have on web, but Get also solves that.
```dart
Get.offAllNamed("/NextScreen?device=phone&id=354&name=Enzo");
```
on your controller/bloc/stateful/stateless class:
```dart
print(Get.parameters['id']);
// out: 354
print(Get.parameters['name']);
// out: Enzo
```
You can also receive NamedParameters with Get easily:
```dart
void main() {
runApp(
GetMaterialApp(
initialRoute: '/',
getPages: [
GetPage(
name: '/',
page: () => MyHomePage(),
),
GetPage(
name: '/profile/',
page: () => MyProfile(),
),
//You can define a different page for routes with arguments, and another without arguments, but for that you must use the slash '/' on the route that will not receive arguments as above.
GetPage(
name: '/profile/:user',
page: () => UserProfile(),
),
GetPage(
name: '/third',
page: () => Third(),
transition: Transition.cupertino
),
],
)
);
}
```
Send data on route name
```dart
Get.toNamed("/profile/34954");
```
On second screen take the data by parameter
```dart
print(Get.parameters['user']);
// out: 34954
```
or send multiple parameters like this
```dart
Get.toNamed("/profile/34954?flag=true&country=italy");
```
or
```dart
var parameters = <String, String>{"flag": "true","country": "italy",};
Get.toNamed("/profile/34954", parameters: parameters);
```
On second screen take the data by parameters as usually
```dart
print(Get.parameters['user']);
print(Get.parameters['flag']);
print(Get.parameters['country']);
// out: 34954 true italy
```
And now, all you need to do is use Get.toNamed() to navigate your named routes, without any context (you can call your routes directly from your BLoC or Controller class), and when your app is compiled to the web, your routes will appear in the url <3
### Middleware
If you want to listen Get events to trigger actions, you can to use routingCallback to it
```dart
GetMaterialApp(
routingCallback: (routing) {
if(routing.current == '/second'){
openAds();
}
}
)
```
If you are not using GetMaterialApp, you can use the manual API to attach Middleware observer.
```dart
void main() {
runApp(
MaterialApp(
onGenerateRoute: Router.generateRoute,
initialRoute: "/",
navigatorKey: Get.key,
navigatorObservers: [
GetObserver(MiddleWare.observer), // HERE !!!
],
),
);
}
```
Create a MiddleWare class
```dart
class MiddleWare {
static observer(Routing routing) {
/// You can listen in addition to the routes, the snackbars, dialogs and bottomsheets on each screen.
///If you need to enter any of these 3 events directly here,
///you must specify that the event is != Than you are trying to do.
if (routing.current == '/second' && !routing.isSnackbar) {
Get.snackbar("Hi", "You are on second route");
} else if (routing.current =='/third'){
print('last route called');
}
}
}
```
Now, use Get on your code:
```dart
class First extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
leading: IconButton(
icon: Icon(Icons.add),
onPressed: () {
Get.snackbar("hi", "i am a modern snackbar");
},
),
title: Text('First Route'),
),
body: Center(
child: ElevatedButton(
child: Text('Open route'),
onPressed: () {
Get.toNamed("/second");
},
),
),
);
}
}
class Second extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
leading: IconButton(
icon: Icon(Icons.add),
onPressed: () {
Get.snackbar("hi", "i am a modern snackbar");
},
),
title: Text('second Route'),
),
body: Center(
child: ElevatedButton(
child: Text('Open route'),
onPressed: () {
Get.toNamed("/third");
},
),
),
);
}
}
class Third extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Third Route"),
),
body: Center(
child: ElevatedButton(
onPressed: () {
Get.back();
},
child: Text('Go back!'),
),
),
);
}
}
```
## Navigation without context
### SnackBars
To have a simple SnackBar with Flutter, you must get the context of Scaffold, or you must use a GlobalKey attached to your Scaffold
```dart
final snackBar = SnackBar(
content: Text('Hi!'),
action: SnackBarAction(
label: 'I am a old and ugly snackbar :(',
onPressed: (){}
),
);
// Find the Scaffold in the widget tree and use
// it to show a SnackBar.
Scaffold.of(context).showSnackBar(snackBar);
```
With Get:
```dart
Get.snackbar('Hi', 'i am a modern snackbar');
```
With Get, all you have to do is call your Get.snackbar from anywhere in your code or customize it however you want!
```dart
Get.snackbar(
"Hey i'm a Get SnackBar!", // title
"It's unbelievable! I'm using SnackBar without context, without boilerplate, without Scaffold, it is something truly amazing!", // message
icon: Icon(Icons.alarm),
shouldIconPulse: true,
onTap:(){},
barBlur: 20,
isDismissible: true,
duration: Duration(seconds: 3),
);
////////// ALL FEATURES //////////
// Color colorText,
// Duration duration,
// SnackPosition snackPosition,
// Widget titleText,
// Widget messageText,
// bool instantInit,
// Widget icon,
// bool shouldIconPulse,
// double maxWidth,
// EdgeInsets margin,
// EdgeInsets padding,
// double borderRadius,
// Color borderColor,
// double borderWidth,
// Color backgroundColor,
// Color leftBarIndicatorColor,
// List<BoxShadow> boxShadows,
// Gradient backgroundGradient,
// TextButton mainButton,
// OnTap onTap,
// bool isDismissible,
// bool showProgressIndicator,
// AnimationController progressIndicatorController,
// Color progressIndicatorBackgroundColor,
// Animation<Color> progressIndicatorValueColor,
// SnackStyle snackStyle,
// Curve forwardAnimationCurve,
// Curve reverseAnimationCurve,
// Duration animationDuration,
// double barBlur,
// double overlayBlur,
// Color overlayColor,
// Form userInputForm
///////////////////////////////////
```
If you prefer the traditional snackbar, or want to customize it from scratch, including adding just one line (Get.snackbar makes use of a mandatory title and message), you can use
`Get.rawSnackbar();` which provides the RAW API on which Get.snackbar was built.
### Dialogs
To open dialog:
```dart
Get.dialog(YourDialogWidget());
```
To open default dialog:
```dart
Get.defaultDialog(
onConfirm: () => print("Ok"),
middleText: "Dialog made in 3 lines of code"
);
```
You can also use Get.generalDialog instead of showGeneralDialog.
For all other Flutter dialog widgets, including cupertinos, you can use Get.overlayContext instead of context, and open it anywhere in your code.
For widgets that don't use Overlay, you can use Get.context.
These two contexts will work in 99% of cases to replace the context of your UI, except for cases where inheritedWidget is used without a navigation context.
### BottomSheets
Get.bottomSheet is like showModalBottomSheet, but don't need of context.
```dart
Get.bottomSheet(
Container(
child: Wrap(
children: <Widget>[
ListTile(
leading: Icon(Icons.music_note),
title: Text('Music'),
onTap: () {}
),
ListTile(
leading: Icon(Icons.videocam),
title: Text('Video'),
onTap: () {},
),
],
),
)
);
```
## Nested Navigation
Get made Flutter's nested navigation even easier.
You don't need the context, and you will find your navigation stack by Id.
- NOTE: Creating parallel navigation stacks can be dangerous. The ideal is not to use NestedNavigators, or to use sparingly. If your project requires it, go ahead, but keep in mind that keeping multiple navigation stacks in memory may not be a good idea for RAM consumption.
See how simple it is:
```dart
Navigator(
key: Get.nestedKey(1), // create a key by index
initialRoute: '/',
onGenerateRoute: (settings) {
if (settings.name == '/') {
return GetPageRoute(
page: () => Scaffold(
appBar: AppBar(
title: Text("Main"),
),
body: Center(
child: TextButton(
color: Colors.blue,
onPressed: () {
Get.toNamed('/second', id:1); // navigate by your nested route by index
},
child: Text("Go to second"),
),
),
),
);
} else if (settings.name == '/second') {
return GetPageRoute(
page: () => Center(
child: Scaffold(
appBar: AppBar(
title: Text("Main"),
),
body: Center(
child: Text("second")
),
),
),
);
}
}
),
```
... ...
* [State Management](#state-management)
+ [Reactive State Manager](#reactive-state-manager)
- [Advantages](#advantages)
- [Maximum performance:](#maximum-performance)
- [Declaring a reactive variable](#declaring-a-reactive-variable)
- [Having a reactive state, is easy.](#having-a-reactive-state-is-easy)
- [Using the values in the view](#using-the-values-in-the-view)
- [Conditions to rebuild](#conditions-to-rebuild)
- [Where .obs can be used](#where-obs-can-be-used)
- [Note about Lists](#note-about-lists)
- [Why i have to use .value](#why-i-have-to-use-value)
- [Obx()](#obx)
- [Workers](#workers)
+ [Simple State Manager](#simple-state-manager)
- [Advantages](#advantages-1)
- [Usage](#usage)
- [How it handles controllers](#how-it-handles-controllers)
- [You won't need StatefulWidgets anymore](#you-wont-need-statefulwidgets-anymore)
- [Why it exists](#why-it-exists)
- [Other ways of using it](#other-ways-of-using-it)
- [Unique IDs](#unique-ids)
+ [Mixing the two state managers](#mixing-the-two-state-managers)
+ [GetBuilder vs GetX vs Obx vs MixinBuilder](#getbuilder-vs-getx-vs-obx-vs-mixinbuilder)
# State Management
GetX does not use Streams or ChangeNotifier like other state managers. Why? In addition to building applications for android, iOS, web, linux, macos and linux, with GetX you can build server applications with the same syntax as Flutter/GetX. In order to improve response time and reduce RAM consumption, we created GetValue and GetStream, which are low latency solutions that deliver a lot of performance, at a low operating cost. We use this base to build all of our resources, including state management.
* _Complexity_: Some state managers are complex and have a lot of boilerplate. With GetX you don't have to define a class for each event, the code is highly clean and clear, and you do a lot more by writing less. Many people have given up on Flutter because of this topic, and they now finally have a stupidly simple solution for managing states.
* _No code generators_: You spend half your development time writing your application logic. Some state managers rely on code generators to have minimally readable code. Changing a variable and having to run build_runner can be unproductive, and often the waiting time after a flutter clean will be long, and you will have to drink a lot of coffee.
With GetX everything is reactive, and nothing depends on code generators, increasing your productivity in all aspects of your development.
* _It does not depend on context_: You probably already needed to send the context of your view to a controller, making the View's coupling with your business logic high. You have probably had to use a dependency for a place that has no context, and had to pass the context through various classes and functions. This just doesn't exist with GetX. You have access to your controllers from within your controllers without any context. You don't need to send the context by parameter for literally nothing.
* _Granular control_: most state managers are based on ChangeNotifier. ChangeNotifier will notify all widgets that depend on it when notifyListeners is called. If you have 40 widgets on one screen, which have a variable of your ChangeNotifier class, when you update one, all of them will be rebuilt.
With GetX, even nested widgets are respected. If you have Obx watching your ListView, and another watching a checkbox inside the ListView, when changing the CheckBox value, only it will be updated, when changing the List value, only the ListView will be updated.
* _It only reconstructs if its variable REALLY changes_: GetX has flow control, that means if you display a Text with 'Paola', if you change the observable variable to 'Paola' again, the widget will not be reconstructed. That's because GetX knows that 'Paola' is already being displayed in Text, and will not do unnecessary reconstructions.
Most (if not all) current state managers will rebuild on the screen.
## Reactive State Manager
Reactive programming can alienate many people because it is said to be complicated. GetX turns reactive programming into something quite simple:
* You won't need to create StreamControllers.
* You won't need to create a StreamBuilder for each variable
* You will not need to create a class for each state.
* You will not need to create a get for an initial value.
Reactive programming with Get is as easy as using setState.
Let's imagine that you have a name variable and want that every time you change it, all widgets that use it are automatically changed.
This is your count variable:
``` dart
var name = 'Jonatas Borges';
```
To make it observable, you just need to add ".obs" to the end of it:
``` dart
var name = 'Jonatas Borges'.obs;
```
That's all. It's *that* simple.
From now on, we might refer to this reactive-".obs"(ervables) variables as _Rx_.
What did we do under the hood? We created a `Stream` of `String` s, assigned the initial value `"Jonatas Borges"` , we notified all widgets that use `"Jonatas Borges"` that they now "belong" to this variable, and when the _Rx_ value changes, they will have to change as well.
This is the **magic of GetX**, thanks to Dart's capabilities.
But, as we know, a `Widget` can only be changed if it is inside a function, because static classes do not have the power to "auto-change".
You will need to create a `StreamBuilder` , subscribe to this variable to listen for changes, and create a "cascade" of nested `StreamBuilder` if you want to change several variables in the same scope, right?
No, you don't need a `StreamBuilder` , but you are right about static classes.
Well, in the view, we usually have a lot of boilerplate when we want to change a specific Widget, that's the Flutter way.
With **GetX** you can also forget about this boilerplate code.
`StreamBuilder( … )` ? `initialValue: …` ? `builder: …` ? Nope, you just need to place this variable inside an `Obx()` Widget.
``` dart
Obx (() => Text (controller.name));
```
_What do you need to memorize?_ Only `Obx(() =>` .
You are just passing that Widget through an arrow-function into an `Obx()` (the "Observer" of the _Rx_).
`Obx` is pretty smart, and will only change if the value of `controller.name` changes.
If `name` is `"John"` , and you change it to `"John"` ( `name.value = "John"` ), as it's the same `value` as before, nothing will change on the screen, and `Obx` , to save resources, will simply ignore the new value and not rebuild the Widget. **Isn't that amazing?**
> So, what if I have 5 _Rx_ (observable) variables within an `Obx` ?
It will just update when **any** of them changes.
> And if I have 30 variables in a class, when I update one, will it update **all** the variables that are in that class?
Nope, just the **specific Widget** that uses that _Rx_ variable.
So, **GetX** only updates the screen, when the _Rx_ variable changes it's value.
```
final isOpen = false.obs;
// NOTHING will happen... same value.
void onButtonTap() => isOpen.value=false;
```
### Advantages
**GetX()** helps you when you need **granular** control over what's being updated.
If you do not need `unique IDs` , because all your variables will be modified when you perform an action, then use `GetBuilder` ,
because it's a Simple State Updater (in blocks, like `setState()` ), made in just a few lines of code.
It was made simple, to have the least CPU impact, and just to fulfill a single purpose (a _State_ rebuild) and spend the minimum resources possible.
If you need a **powerful** State Manager, you can't go wrong with **GetX**.
It doesn't work with variables, but __flows__, everything in it are `Streams` under the hood.
You can use _rxDart_ in conjunction with it, because everything are `Streams`,
you can listen to the `event` of each "_Rx_ variable",
because everything in it are `Streams`.
It is literally a _BLoC_ approach, easier than _MobX_, and without code generators or decorations.
You can turn **anything** into an _"Observable"_ with just a `.obs` .
### Maximum performance:
In addition to having a smart algorithm for minimal rebuilds, **GetX** uses comparators
to make sure the State has changed.
If you experience any errors in your app, and send a duplicate change of State,
**GetX** will ensure it will not crash.
With **GetX** the State only changes if the `value` change.
That's the main difference between **GetX**, and using _ `computed` from MobX_.
When joining two __observables__, and one changes; the listener of that _observable_ will change as well.
With **GetX**, if you join two variables, `GetX()` (similar to `Observer()` ) will only rebuild if it implies a real change of State.
### Declaring a reactive variable
You have 3 ways to turn a variable into an "observable".
1 - The first is using **`Rx{Type}`**.
``` dart
// initial value is recommended, but not mandatory
final name = RxString('');
final isLogged = RxBool(false);
final count = RxInt(0);
final balance = RxDouble(0.0);
final items = RxList<String>([]);
final myMap = RxMap<String, int>({});
```
2 - The second is to use **`Rx`** and use Darts Generics, `Rx<Type>`
``` dart
final name = Rx<String>('');
final isLogged = Rx<Bool>(false);
final count = Rx<Int>(0);
final balance = Rx<Double>(0.0);
final number = Rx<Num>(0);
final items = Rx<List<String>>([]);
final myMap = Rx<Map<String, int>>({});
// Custom classes - it can be any class, literally
final user = Rx<User>();
```
3 - The third, more practical, easier and preferred approach, just add **`.obs`** as a property of your `value` :
``` dart
final name = ''.obs;
final isLogged = false.obs;
final count = 0.obs;
final balance = 0.0.obs;
final number = 0.obs;
final items = <String>[].obs;
final myMap = <String, int>{}.obs;
// Custom classes - it can be any class, literally
final user = User().obs;
```
##### Having a reactive state, is easy.
As we know, _Dart_ is now heading towards _null safety_.
To be prepared, from now on, you should always start your _Rx_ variables with an **initial value**.
> Transforming a variable into an _observable_ + _initial value_ with **GetX** is the simplest, and most practical approach.
You will literally add a " `.obs` " to the end of your variable, and **that’s it**, you’ve made it observable,
and its `.value` , well, will be the _initial value_).
### Using the values in the view
``` dart
// controller file
final count1 = 0.obs;
final count2 = 0.obs;
int get sum => count1.value + count2.value;
```
``` dart
// view file
GetX<Controller>(
builder: (controller) {
print("count 1 rebuild");
return Text('${controller.count1.value}');
},
),
GetX<Controller>(
builder: (controller) {
print("count 2 rebuild");
return Text('${controller.count2.value}');
},
),
GetX<Controller>(
builder: (controller) {
print("count 3 rebuild");
return Text('${controller.sum}');
},
),
```
If we increment `count1.value++` , it will print:
* `count 1 rebuild`
* `count 3 rebuild`
because `count1` has a value of `1` , and `1 + 0 = 1` , changing the `sum` getter value.
If we change `count2.value++` , it will print:
* `count 2 rebuild`
* `count 3 rebuild`
because `count2.value` changed, and the result of the `sum` is now `2` .
* NOTE: By default, the very first event will rebuild the widget, even if it is the same `value`.
This behavior exists due to Boolean variables.
Imagine you did this:
``` dart
var isLogged = false.obs;
```
And then, you checked if a user is "logged in" to trigger an event in `ever` .
``` dart
@override
onInit() async {
ever(isLogged, fireRoute);
isLogged.value = await Preferences.hasToken();
}
fireRoute(logged) {
if (logged) {
Get.off(Home());
} else {
Get.off(Login());
}
}
```
if `hasToken` was `false` , there would be no change to `isLogged` , so `ever()` would never be called.
To avoid this type of behavior, the first change to an _observable_ will always trigger an event,
even if it contains the same `.value` .
You can remove this behavior if you want, using:
`isLogged.firstRebuild = false;`
### Conditions to rebuild
In addition, Get provides refined state control. You can condition an event (such as adding an object to a list), on a certain condition.
``` dart
// First parameter: condition, must return true or false.
// Second parameter: the new value to apply if the condition is true.
list.addIf(item < limit, item);
```
Without decorations, without a code generator, without complications :smile:
Do you know Flutter's counter app? Your Controller class might look like this:
``` dart
class CountController extends GetxController {
final count = 0.obs;
}
```
With a simple:
``` dart
controller.count.value++
```
You could update the counter variable in your UI, regardless of where it is stored.
### Where .obs can be used
You can transform anything on obs. Here are two ways of doing it:
* You can convert your class values to obs
``` dart
class RxUser {
final name = "Camila".obs;
final age = 18.obs;
}
```
* or you can convert the entire class to be an observable
``` dart
class User {
User({String name, int age});
var name;
var age;
}
// when instantianting:
final user = User(name: "Camila", age: 18).obs;
```
### Note about Lists
Lists are completely observable as are the objects within it. That way, if you add a value to a list, it will automatically rebuild the widgets that use it.
You also don't need to use ".value" with lists, the amazing dart api allowed us to remove that.
Unfortunaly primitive types like String and int cannot be extended, making the use of .value mandatory, but that won't be a problem if you work with gets and setters for these.
``` dart
// On the controller
final String title = 'User Info:'.obs
final list = List<User>().obs;
// on the view
Text(controller.title.value), // String need to have .value in front of it
ListView.builder (
itemCount: controller.list.length // lists don't need it
)
```
When you are making your own classes observable, there is a different way to update them:
``` dart
// on the model file
// we are going to make the entire class observable instead of each attribute
class User() {
User({this.name = '', this.age = 0});
String name;
int age;
}
// on the controller file
final user = User().obs;
// when you need to update the user variable:
user.update( (user) { // this parameter is the class itself that you want to update
user.name = 'Jonny';
user.age = 18;
});
// an alternative way of update the user variable:
user(User(name: 'João', age: 35));
// on view:
Obx(()=> Text("Name ${user.value.name}: Age: ${user.value.age}"))
// you can also access the model values without the .value:
user().name; // notice that is the user variable, not the class (variable has lowercase u)
```
You don't have to work with sets if you don't want to. you can use the "assign 'and" assignAll "api.
The "assign" api will clear your list, and add a single object that you want to start there.
The "assignAll" api will clear the existing list and add any iterable objects that you inject into it.
### Why i have to use .value
We could remove the obligation to use 'value' to `String` and `int` with a simple decoration and code generator, but the purpose of this library is precisely avoid external dependencies. We want to offer an environment ready for programming, involving the essentials (management of routes, dependencies and states), in a simple, lightweight and performant way, without a need of an external package.
You can literally add 3 letters to your pubspec (get) and a colon and start programming. All solutions included by default, from route management to state management, aim at ease, productivity and performance.
The total weight of this library is less than that of a single state manager, even though it is a complete solution, and that is what you must understand.
If you are bothered by `.value` , and like a code generator, MobX is a great alternative, and you can use it in conjunction with Get. For those who want to add a single dependency in pubspec and start programming without worrying about the version of a package being incompatible with another, or if the error of a state update is coming from the state manager or dependency, or still, do not want to worrying about the availability of controllers, whether literally "just programming", get is just perfect.
If you have no problem with the MobX code generator, or have no problem with the BLoC boilerplate, you can simply use Get for routes, and forget that it has state manager. Get SEM and RSM were born out of necessity, my company had a project with more than 90 controllers, and the code generator simply took more than 30 minutes to complete its tasks after a Flutter Clean on a reasonably good machine, if your project it has 5, 10, 15 controllers, any state manager will supply you well. If you have an absurdly large project, and code generator is a problem for you, you have been awarded this solution.
Obviously, if someone wants to contribute to the project and create a code generator, or something similar, I will link in this readme as an alternative, my need is not the need for all devs, but for now I say, there are good solutions that already do that, like MobX.
### Obx()
Typing in Get using Bindings is unnecessary. you can use the Obx widget instead of GetX which only receives the anonymous function that creates a widget.
Obviously, if you don't use a type, you will need to have an instance of your controller to use the variables, or use `Get.find<Controller>()` .value or Controller.to.value to retrieve the value.
### Workers
Workers will assist you, triggering specific callbacks when an event occurs.
``` dart
/// Called every time `count1` changes.
ever(count1, (_) => print("$_ has been changed"));
/// Called only first time the variable $_ is changed
once(count1, (_) => print("$_ was changed once"));
/// Anti DDos - Called every time the user stops typing for 1 second, for example.
debounce(count1, (_) => print("debouce$_"), time: Duration(seconds: 1));
/// Ignore all changes within 1 second.
interval(count1, (_) => print("interval $_"), time: Duration(seconds: 1));
```
All workers (except `debounce` ) have a `condition` named parameter, which can be a `bool` or a callback that returns a `bool` .
This `condition` defines when the `callback` function executes.
All workers returns a `Worker` instance, that you can use to cancel ( via `dispose()` ) the worker.
* **`ever`**
is called every time the _Rx_ variable emits a new value.
* **`everAll`**
Much like `ever` , but it takes a `List` of _Rx_ values Called every time its variable is changed. That's it.
* **`once`**
'once' is called only the first time the variable has been changed.
* **`debounce`**
'debounce' is very useful in search functions, where you only want the API to be called when the user finishes typing. If the user types "Jonny", you will have 5 searches in the APIs, by the letter J, o, n, n, and y. With Get this does not happen, because you will have a "debounce" Worker that will only be triggered at the end of typing.
* **`interval`**
'interval' is different from the debouce. debouce if the user makes 1000 changes to a variable within 1 second, he will send only the last one after the stipulated timer (the default is 800 milliseconds). Interval will instead ignore all user actions for the stipulated period. If you send events for 1 minute, 1000 per second, debounce will only send you the last one, when the user stops strafing events. interval will deliver events every second, and if set to 3 seconds, it will deliver 20 events that minute. This is recommended to avoid abuse, in functions where the user can quickly click on something and get some advantage (imagine that the user can earn coins by clicking on something, if he clicked 300 times in the same minute, he would have 300 coins, using interval, you you can set a time frame for 3 seconds, and even then clicking 300 or a thousand times, the maximum he would get in 1 minute would be 20 coins, clicking 300 or 1 million times). The debounce is suitable for anti-DDos, for functions like search where each change to onChange would cause a query to your api. Debounce will wait for the user to stop typing the name, to make the request. If it were used in the coin scenario mentioned above, the user would only win 1 coin, because it is only executed, when the user "pauses" for the established time.
* NOTE: Workers should always be used when starting a Controller or Class, so it should always be on onInit (recommended), Class constructor, or the initState of a StatefulWidget (this practice is not recommended in most cases, but it shouldn't have any side effects).
## Simple State Manager
Get has a state manager that is extremely light and easy, which does not use ChangeNotifier, will meet the need especially for those new to Flutter, and will not cause problems for large applications.
GetBuilder is aimed precisely at multiple state control. Imagine that you added 30 products to a cart, you click delete one, at the same time that the list is updated, the price is updated and the badge in the shopping cart is updated to a smaller number. This type of approach makes GetBuilder killer, because it groups states and changes them all at once without any "computational logic" for that. GetBuilder was created with this type of situation in mind, since for ephemeral change of state, you can use setState and you would not need a state manager for this.
That way, if you want an individual controller, you can assign IDs for that, or use GetX. This is up to you, remembering that the more "individual" widgets you have, the more the performance of GetX will stand out, while the performance of GetBuilder should be superior, when there is multiple change of state.
### Advantages
1. Update only the required widgets.
2. Does not use changeNotifier, it is the state manager that uses less memory (close to 0mb).
3. Forget StatefulWidget! With Get you will never need it. With the other state managers, you will probably have to use a StatefulWidget to get the instance of your Provider, BLoC, MobX Controller, etc. But have you ever stopped to think that your appBar, your scaffold, and most of the widgets that are in your class are stateless? So why save the state of an entire class, if you can only save the state of the Widget that is stateful? Get solves that, too. Create a Stateless class, make everything stateless. If you need to update a single component, wrap it with GetBuilder, and its state will be maintained.
4. Organize your project for real! Controllers must not be in your UI, place your TextEditController, or any controller you use within your Controller class.
5. Do you need to trigger an event to update a widget as soon as it is rendered? GetBuilder has the property "initState", just like StatefulWidget, and you can call events from your controller, directly from it, no more events being placed in your initState.
6. Do you need to trigger an action like closing streams, timers and etc? GetBuilder also has the dispose property, where you can call events as soon as that widget is destroyed.
7. Use streams only if necessary. You can use your StreamControllers inside your controller normally, and use StreamBuilder also normally, but remember, a stream reasonably consumes memory, reactive programming is beautiful, but you shouldn't abuse it. 30 streams open simultaneously can be worse than changeNotifier (and changeNotifier is very bad).
8. Update widgets without spending ram for that. Get stores only the GetBuilder creator ID, and updates that GetBuilder when necessary. The memory consumption of the get ID storage in memory is very low even for thousands of GetBuilders. When you create a new GetBuilder, you are actually sharing the state of GetBuilder that has a creator ID. A new state is not created for each GetBuilder, which saves A LOT OF ram for large applications. Basically your application will be entirely Stateless, and the few Widgets that will be Stateful (within GetBuilder) will have a single state, and therefore updating one will update them all. The state is just one.
9. Get is omniscient and in most cases it knows exactly the time to take a controller out of memory. You should not worry about when to dispose of a controller, Get knows the best time to do this.
### Usage
``` dart
// Create controller class and extends GetxController
class Controller extends GetxController {
int counter = 0;
void increment() {
counter++;
update(); // use update() to update counter variable on UI when increment be called
}
}
// On your Stateless/Stateful class, use GetBuilder to update Text when increment be called
GetBuilder<Controller>(
init: Controller(), // INIT IT ONLY THE FIRST TIME
builder: (_) => Text(
'${_.counter}',
),
)
//Initialize your controller only the first time. The second time you are using ReBuilder for the same controller, do not use it again. Your controller will be automatically removed from memory as soon as the widget that marked it as 'init' is deployed. You don't have to worry about that, Get will do it automatically, just make sure you don't start the same controller twice.
```
**Done!**
* You have already learned how to manage states with Get.
* Note: You may want a larger organization, and not use the init property. For that, you can create a class and extends Bindings class, and within it mention the controllers that will be created within that route. Controllers will not be created at that time, on the contrary, this is just a statement, so that the first time you use a Controller, Get will know where to look. Get will remain lazyLoad, and will continue to dispose Controllers when they are no longer needed. See the pub.dev example to see how it works.
If you navigate many routes and need data that was in your previously used controller, you just need to use GetBuilder Again (with no init):
``` dart
class OtherClass extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: GetBuilder<Controller>(
builder: (s) => Text('${s.counter}'),
),
),
);
}
```
If you need to use your controller in many other places, and outside of GetBuilder, just create a get in your controller and have it easily. (or use `Get.find<Controller>()` )
``` dart
class Controller extends GetxController {
/// You do not need that. I recommend using it just for ease of syntax.
/// with static method: Controller.to.increment();
/// with no static method: Get.find<Controller>().increment();
/// There is no difference in performance, nor any side effect of using either syntax. Only one does not need the type, and the other the IDE will autocomplete it.
static Controller get to => Get.find(); // add this line
int counter = 0;
void increment() {
counter++;
update();
}
}
```
And then you can access your controller directly, that way:
``` dart
FloatingActionButton(
onPressed: () {
Controller.to.increment(),
} // This is incredibly simple!
child: Text("${Controller.to.counter}"),
),
```
When you press FloatingActionButton, all widgets that are listening to the 'counter' variable will be updated automatically.
### How it handles controllers
Let's say we have this:
`Class a => Class B (has controller X) => Class C (has controller X)`
In class A the controller is not yet in memory, because you have not used it yet (Get is lazyLoad). In class B you used the controller, and it entered memory. In class C you used the same controller as in class B, Get will share the state of controller B with controller C, and the same controller is still in memory. If you close screen C and screen B, Get will automatically take controller X out of memory and free up resources, because Class a is not using the controller. If you navigate to B again, controller X will enter memory again, if instead of going to class C, you return to class A again, Get will take the controller out of memory in the same way. If class C didn't use the controller, and you took class B out of memory, no class would be using controller X and likewise it would be disposed of. The only exception that can mess with Get, is if you remove B from the route unexpectedly, and try to use the controller in C. In this case, the creator ID of the controller that was in B was deleted, and Get was programmed to remove it from memory every controller that has no creator ID. If you intend to do this, add the "autoRemove: false" flag to class B's GetBuilder and use adoptID = true; in class C's GetBuilder.
### You won't need StatefulWidgets anymore
Using StatefulWidgets means storing the state of entire screens unnecessarily, even because if you need to minimally rebuild a widget, you will embed it in a Consumer/Observer/BlocProvider/GetBuilder/GetX/Obx, which will be another StatefulWidget.
The StatefulWidget class is a class larger than StatelessWidget, which will allocate more RAM, and this may not make a significant difference between one or two classes, but it will most certainly do when you have 100 of them!
Unless you need to use a mixin, like TickerProviderStateMixin, it will be totally unnecessary to use a StatefulWidget with Get.
You can call all methods of a StatefulWidget directly from a GetBuilder.
If you need to call initState() or dispose() method for example, you can call them directly;
``` dart
GetBuilder<Controller>(
initState: (_) => Controller.to.fetchApi(),
dispose: (_) => Controller.to.closeStreams(),
builder: (s) => Text('${s.username}'),
),
```
A much better approach than this is to use the onInit() and onClose() method directly from your controller.
``` dart
@override
void onInit() {
fetchApi();
super.onInit();
}
```
* NOTE: If you want to start a method at the moment the controller is called for the first time, you DON'T NEED to use constructors for this, in fact, using a performance-oriented package like Get, this borders on bad practice, because it deviates from the logic in which the controllers are created or allocated (if you create an instance of this controller, the constructor will be called immediately, you will be populating a controller before it is even used, you are allocating memory without it being in use, this definitely hurts the principles of this library). The onInit() methods; and onClose(); were created for this, they will be called when the Controller is created, or used for the first time, depending on whether you are using Get.lazyPut or not. If you want, for example, to make a call to your API to populate data, you can forget about the old-fashioned method of initState/dispose, just start your call to the api in onInit, and if you need to execute any command like closing streams, use the onClose() for that.
### Why it exists
The purpose of this package is precisely to give you a complete solution for navigation of routes, management of dependencies and states, using the least possible dependencies, with a high degree of decoupling. Get engages all high and low level Flutter APIs within itself, to ensure that you work with the least possible coupling. We centralize everything in a single package, to ensure that you don't have any kind of coupling in your project. That way, you can put only widgets in your view, and leave the part of your team that works with the business logic free, to work with the business logic without depending on any element of the View. This provides a much cleaner working environment, so that part of your team works only with widgets, without worrying about sending data to your controller, and part of your team works only with the business logic in its breadth, without depending on no element of the view.
So to simplify this:
You don't need to call methods in initState and send them by parameter to your controller, nor use your controller constructor for that, you have the onInit() method that is called at the right time for you to start your services.
You do not need to call the device, you have the onClose() method that will be called at the exact moment when your controller is no longer needed and will be removed from memory. That way, leave views for widgets only, refrain from any kind of business logic from it.
Do not call a dispose method inside GetxController, it will not do anything, remember that the controller is not a Widget, you should not "dispose" it, and it will be automatically and intelligently removed from memory by Get. If you used any stream on it and want to close it, just insert it into the close method. Example:
``` dart
class Controller extends GetxController {
StreamController<User> user = StreamController<User>();
StreamController<String> name = StreamController<String>();
/// close stream = onClose method, not dispose.
@override
void onClose() {
user.close();
name.close();
super.onClose();
}
}
```
Controller life cycle:
* onInit() where it is created.
* onClose() where it is closed to make any changes in preparation for the delete method
* deleted: you do not have access to this API because it is literally removing the controller from memory. It is literally deleted, without leaving any trace.
### Other ways of using it
You can use Controller instance directly on GetBuilder value:
``` dart
GetBuilder<Controller>(
init: Controller(),
builder: (value) => Text(
'${value.counter}', //here
),
),
```
You may also need an instance of your controller outside of your GetBuilder, and you can use these approaches to achieve this:
``` dart
class Controller extends GetxController {
static Controller get to => Get.find();
[...]
}
// on you view:
GetBuilder<Controller>(
init: Controller(), // use it only first time on each controller
builder: (_) => Text(
'${Controller.to.counter}', //here
)
),
```
or
``` dart
class Controller extends GetxController {
// static Controller get to => Get.find(); // with no static get
[...]
}
// on stateful/stateless class
GetBuilder<Controller>(
init: Controller(), // use it only first time on each controller
builder: (_) => Text(
'${Get.find<Controller>().counter}', //here
),
),
```
* You can use "non-canonical" approaches to do this. If you are using some other dependency manager, like get_it, modular, etc., and just want to deliver the controller instance, you can do this:
``` dart
Controller controller = Controller();
[...]
GetBuilder<Controller>(
init: controller, //here
builder: (_) => Text(
'${controller.counter}', // here
),
),
```
### Unique IDs
If you want to refine a widget's update control with GetBuilder, you can assign them unique IDs:
``` dart
GetBuilder<Controller>(
id: 'text'
init: Controller(), // use it only first time on each controller
builder: (_) => Text(
'${Get.find<Controller>().counter}', //here
),
),
```
And update it this form:
``` dart
update(['text']);
```
You can also impose conditions for the update:
``` dart
update(['text'], counter < 10);
```
GetX does this automatically and only reconstructs the widget that uses the exact variable that was changed, if you change a variable to the same as the previous one and that does not imply a change of state , GetX will not rebuild the widget to save memory and CPU cycles (3 is being displayed on the screen, and you change the variable to 3 again. In most state managers, this will cause a new rebuild, but with GetX the widget will only is rebuilt again, if in fact his state has changed).
## Mixing the two state managers
Some people opened a feature request, as they wanted to use only one type of reactive variable, and the other mechanics, and needed to insert an Obx into a GetBuilder for this. Thinking about it MixinBuilder was created. It allows both reactive changes by changing ".obs" variables, and mechanical updates via update(). However, of the 4 widgets he is the one that consumes the most resources, since in addition to having a Subscription to receive change events from his children, he subscribes to the update method of his controller.
Extending GetxController is important, as they have life cycles, and can "start" and "end" events in their onInit() and onClose() methods. You can use any class for this, but I strongly recommend you use the GetxController class to place your variables, whether they are observable or not.
## StateMixin
Another way to handle your `UI` state is use the `StateMixin<T>` .
To implement it, use the `with` to add the `StateMixin<T>`
to your controller which allows a T model.
``` dart
class Controller extends GetController with StateMixin<User>{}
```
The `change()` method change the State whenever we want.
Just pass the data and the status in this way:
```dart
change(data, status: RxStatus.success());
```
RxStatus allow these status:
``` dart
RxStatus.loading();
RxStatus.success();
RxStatus.empty();
RxStatus.error('message');
```
To represent it in the UI, use:
```dart
class OtherClass extends GetView<Controller> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: controller.obx(
(state)=>Text(state.name),
// here you can put your custom loading indicator, but
// by default would be Center(child:CircularProgressIndicator())
onLoading: CustomLoadingIndicator(),
onEmpty: Text('No data found'),
// here also you can set your own error widget, but by
// default will be an Center(child:Text(error))
onError: (error)=>Text(error),
),
);
}
```
## GetBuilder vs GetX vs Obx vs MixinBuilder
In a decade working with programming I was able to learn some valuable lessons.
My first contact with reactive programming was so "wow, this is incredible" and in fact reactive programming is incredible.
However, it is not suitable for all situations. Often all you need is to change the state of 2 or 3 widgets at the same time, or an ephemeral change of state, in which case reactive programming is not bad, but it is not appropriate.
Reactive programming has a higher RAM consumption that can be compensated for by the individual workflow, which will ensure that only one widget is rebuilt and when necessary, but creating a list with 80 objects, each with several streams is not a good one idea. Open the dart inspect and check how much a StreamBuilder consumes, and you'll understand what I'm trying to tell you.
With that in mind, I created the simple state manager. It is simple, and that is exactly what you should demand from it: updating state in blocks in a simple way, and in the most economical way.
GetBuilder is very economical in RAM, and there is hardly a more economical approach than him (at least I can't imagine one, if it exists, please let us know).
However, GetBuilder is still a mechanical state manager, you need to call update() just like you would need to call Provider's notifyListeners().
There are other situations where reactive programming is really interesting, and not working with it is the same as reinventing the wheel. With that in mind, GetX was created to provide everything that is most modern and advanced in a state manager. It updates only what is necessary and when necessary, if you have an error and send 300 state changes simultaneously, GetX will filter and update the screen only if the state actually changes.
GetX is still more economical than any other reactive state manager, but it consumes a little more RAM than GetBuilder. Thinking about it and aiming to maximize the consumption of resources that Obx was created. Unlike GetX and GetBuilder, you will not be able to initialize a controller inside an Obx, it is just a Widget with a StreamSubscription that receives change events from your children, that's all. It is more economical than GetX, but loses to GetBuilder, which was to be expected, since it is reactive, and GetBuilder has the most simplistic approach that exists, of storing a widget's hashcode and its StateSetter. With Obx you don't need to write your controller type, and you can hear the change from multiple different controllers, but it needs to be initialized before, either using the example approach at the beginning of this readme, or using the Bindings class.
... ...