Observing "MemoryWarningNotification" and proxying it up to the DeviceEventEmitter

Examples/UIExplorer/AppStateIOSExample.js

@@ -28,13 +28,19 @@ var AppStateSubscription = React.createClass({
     return {
       appState: AppStateIOS.currentState,
       previousAppStates: [],
+      memoryWarnings: 0,
     };
   },
   componentDidMount: function() {
     AppStateIOS.addEventListener('change', this._handleAppStateChange);
+    AppStateIOS.addEventListener('memoryWarning', this._handleMemoryWarning);
   },
   componentWillUnmount: function() {
     AppStateIOS.removeEventListener('change', this._handleAppStateChange);
+    AppStateIOS.removeEventListener('memoryWarning', this._handleMemoryWarning);
+  },
+  _handleMemoryWarning: function() {
+    this.setState({memoryWarnings: this.state.memoryWarnings + 1})
   },
   _handleAppStateChange: function(appState) {
     var previousAppStates = this.state.previousAppStates.slice();
@@ -45,6 +51,13 @@ var AppStateSubscription = React.createClass({
     });
   },
   render() {
+    if (this.props.showMemoryWarnings) {
+      return (
+        <View>
+          <Text>{this.state.memoryWarnings}</Text>
+        </View>
+      );
+    }
     if (this.props.showCurrentOnly) {
       return (
         <View>
@@ -77,4 +90,9 @@ exports.examples = [
     title: 'Previous states:',
     render(): ReactElement { return <AppStateSubscription showCurrentOnly={false} />; }
   },
+  {
+    title: 'Memory Warnings',
+    description: "In the simulator, hit Shift+Command+M to simulate a memory warning.",
+    render(): ReactElement { return <AppStateSubscription showMemoryWarnings={true} />; }
+  },
 ];

Libraries/AppStateIOS/AppStateIOS.ios.js

@@ -16,10 +16,12 @@ var RCTDeviceEventEmitter = require('RCTDeviceEventEmitter');
 var RCTAppState = NativeModules.AppState;
 
 var logError = require('logError');
+var invariant = require('invariant');
 
-var DEVICE_APPSTATE_EVENT = 'appStateDidChange';
-
-var _appStateHandlers = {};
+var _eventHandlers = {
+  change: new Map(),
+  memoryWarning: new Map(),
+};
 
 /**
  * `AppStateIOS` can tell you if the app is in the foreground or background,
@@ -82,12 +84,23 @@ var AppStateIOS = {
     type: string,
     handler: Function
   ) {
-    _appStateHandlers[handler] = RCTDeviceEventEmitter.addListener(
-      DEVICE_APPSTATE_EVENT,
-      (appStateData) => {
-        handler(appStateData.app_state);
-      }
+    invariant(
+      ['change', 'memoryWarning'].indexOf(type) !== -1,
+      'Trying to subscribe to unknown event: "%s"', type
     );
+    if (type === 'change') {
+      _eventHandlers[type].set(handler, RCTDeviceEventEmitter.addListener(
+        'appStateDidChange',
+        (appStateData) => {
+          handler(appStateData.app_state);
+        }
+      ));
+    } else if (type === 'memoryWarning') {
+      _eventHandlers[type].set(handler, RCTDeviceEventEmitter.addListener(
+        'memoryWarning',
+        handler
+      ));
+    }
   },
 
   /**
@@ -97,11 +110,15 @@ var AppStateIOS = {
     type: string,
     handler: Function
   ) {
-    if (!_appStateHandlers[handler]) {
+    invariant(
+      ['change', 'memoryWarning'].indexOf(type) !== -1,
+      'Trying to remove listener for unknown event: "%s"', type
+    );
+    if (!_eventHandlers[type].has(handler)) {
       return;
     }
-    _appStateHandlers[handler].remove();
-    _appStateHandlers[handler] = null;
+    _eventHandlers[type].get(handler).remove();
+    _eventHandlers[type].delete(handler);
   },
 
   currentState: (null : ?String),
@@ -109,7 +126,7 @@ var AppStateIOS = {
 };
 
 RCTDeviceEventEmitter.addListener(
-  DEVICE_APPSTATE_EVENT,
+  'appStateDidChange',
   (appStateData) => {
     AppStateIOS.currentState = appStateData.app_state;
   }

React/Modules/RCTAppState.m

@@ -53,11 +53,21 @@ RCT_EXPORT_MODULE()
                                                selector:@selector(handleAppStateDidChange)
                                                    name:name
                                                  object:nil];
+
+      [[NSNotificationCenter defaultCenter] addObserver:self
+                                               selector:@selector(handleMemoryWarning)
+                                                   name:UIApplicationDidReceiveMemoryWarningNotification
+                                                 object:nil];
     }
   }
   return self;
 }
 
+- (void)handleMemoryWarning
+{
+  [_bridge.eventDispatcher sendDeviceEventWithName:@"memoryWarning"
+                                              body:nil];
+}
 
 - (void)dealloc
 {