Prevent double-observers for the idleTimerDisabled value change (#108)

* Add a additional class to wrap observers for the sharedApplication.idleTimerDisabled

* CL & version

* Align wording with other entries

Co-authored-by: creativecreatorormaybenot <creativecreatorormaybenot@gmail.com>

+## 0.5.1
+
+* Resolved a crash on iOS which was caused by 2 observers on idleTimerDisabled.
+
 ## 0.5.0+2
 
 * Fixed example app builds on macOS.

@@ -21,8 +21,8 @@ EXTERNAL SOURCES:
 SPEC CHECKSUMS:
   Flutter: 434fef37c0980e73bb6479ef766c45957d4b510c
   integration_test: 5ed24a436eb7ec17b6a13046e9bf7ca4a404e59e
-  wakelock: bfc7955c418d0db797614075aabbc58a39ab5107
+  wakelock: d0fc7c864128eac40eba1617cb5264d9c940b46f
 
 PODFILE CHECKSUM: 8e679eca47255a8ca8067c4c67aab20e64cb974d
 
-COCOAPODS: 1.10.0
+COCOAPODS: 1.10.1

@@ -2,6 +2,6 @@
 <Workspace
    version = "1.0">
    <FileRef
-      location = "group:Runner.xcodeproj">
+      location = "self:">
    </FileRef>
 </Workspace>

+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface IdleTimerDisabledObserver : NSObject
+
+@property BOOL enable;
+
++ (IdleTimerDisabledObserver*)singleInstance;
+
+- (void) beginObserving;
+
+- (void) endObserving;
+
+@end
+
+NS_ASSUME_NONNULL_END

+#import "IdleTimerDisabledObserver.h"
+
+@interface IdleTimerDisabledObserver() {
+  int numObservers;
+}
+
+@end
+
+static void * mKeyPathObserverContextApplicationIsIdleTimerDisabled = &mKeyPathObserverContextApplicationIsIdleTimerDisabled;
+
+@implementation IdleTimerDisabledObserver
+
++ (IdleTimerDisabledObserver*)singleInstance {
+  static IdleTimerDisabledObserver *instance = nil;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    instance = [[self alloc] init];
+  });
+  return instance;
+}
+
+- (void)beginObserving {
+  if (numObservers == 0) {
+    [UIApplication.sharedApplication addObserver:self
+                                      forKeyPath:@"idleTimerDisabled"
+                                         options:NSKeyValueObservingOptionNew
+                                         context:mKeyPathObserverContextApplicationIsIdleTimerDisabled];
+  }
+  
+  numObservers ++;
+}
+
+- (void)endObserving {
+  numObservers --;
+  
+  if (numObservers == 0) {
+    [UIApplication.sharedApplication removeObserver:self forKeyPath:@"idleTimerDisabled" context:mKeyPathObserverContextApplicationIsIdleTimerDisabled];
+  }
+}
+
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
+  if (context == mKeyPathObserverContextApplicationIsIdleTimerDisabled) {
+    if (UIApplication.sharedApplication.idleTimerDisabled != self.enable) {
+      UIApplication.sharedApplication.idleTimerDisabled = self.enable;
+    }
+  } else {
+    [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
+  }
+}
+
+
+@end

 #import "WakelockPlugin.h"
+#import "IdleTimerDisabledObserver.h"
 #import "messages.h"
 
-static void * mKeyPathObserverContextApplicationIsIdleTimerDisabled = &mKeyPathObserverContextApplicationIsIdleTimerDisabled;
 
 @interface WakelockPlugin () <FLTWakelockApi>
 
@@ -14,7 +14,7 @@ static void * mKeyPathObserverContextApplicationIsIdleTimerDisabled = &mKeyPathO
   WakelockPlugin* instance = [[WakelockPlugin alloc] init];
   FLTWakelockApiSetup(registrar.messenger, instance);
   
-  [UIApplication.sharedApplication addObserver:instance forKeyPath:@"idleTimerDisabled" options:NSKeyValueObservingOptionNew context:mKeyPathObserverContextApplicationIsIdleTimerDisabled];
+  [[IdleTimerDisabledObserver singleInstance] beginObserving];
 }
 
 - (void)toggle:(FLTToggleMessage*)input error:(FlutterError**)error {
@@ -36,18 +36,14 @@ static void * mKeyPathObserverContextApplicationIsIdleTimerDisabled = &mKeyPathO
   return result;
 }
 
-- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
-  if (context == mKeyPathObserverContextApplicationIsIdleTimerDisabled) {
-    if (UIApplication.sharedApplication.idleTimerDisabled != self.enable) {
-      UIApplication.sharedApplication.idleTimerDisabled = self.enable;
-    }
-  } else {
-    [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
-  }
+- (void)setEnable:(BOOL)enable {
+  [IdleTimerDisabledObserver singleInstance].enable = enable;
+  
+  _enable = enable;
 }
 
 - (void)dealloc {
-  [UIApplication.sharedApplication removeObserver:self forKeyPath:@"idleTimerDisabled" context:mKeyPathObserverContextApplicationIsIdleTimerDisabled];
+  [[IdleTimerDisabledObserver singleInstance] endObserving];
 }
 
 @end

@@ -2,7 +2,7 @@ name: wakelock
 description: >-2
   Plugin that allows you to keep the device screen awake, i.e. prevent the screen from sleeping on
   Android, iOS, macOS, Windows, and web.
-version: 0.5.0+2
+version: 0.5.1
 homepage: https://github.com/creativecreatorormaybenot/wakelock/tree/master/wakelock
 
 environment: