Summary:
The Framework is inconsistent in how listeners are removed in certain classes. This issue has been discussed in https://github.com/facebook/react-native/issues/6493.
For example,
**DeviceEventEmitter**
```javascript
/* Current */
this.keyboardHideObserver = DeviceEventEmitter.addListener('keyboardWillHide', this.keyboardWillHide);
this.keyboardHideObserver.remove();
/* Expected (maybe in addition to the current API) */
DeviceEventEmitter.addListener('keyboardWillHide', this.keyboardWillHide);
DeviceEventEmitter.removeListener('keyboardWillHide', this.keyboardWillHide);
```
**AppStateIOS**
```javascript
AppStateIOS.addEventListener('change', this.handleAppStateChange);
AppStateIOS.removeEventListener('change', this.handleAppStateChange);
```
The API should be consistent, and preferably should allow both ways of removing the listeners.
Currently, developers who tried to use the second way of removing the listeners get an error for function not found. Due to the lack of documenta
Closes https://github.com/facebook/react-native/pull/6884
Differential Revision: D3341235
Pulled By: nicklockwood
fbshipit-source-id: 87431e8b667f46ad002d4a6e3ca07cbc1e6b4007
Summary:
The `EmitterSubscription.remove()` method was previously calling `this.subscriber.removeSubscription(this)` directly, bypassing the mechanism in `NativeEventEmitter` that keeps track of the number of subscriptions.
This meant that native event modules (subclasses of `RCTEventEmitter`) would keep sending events even after all the listeners had been removed. This wasn't a huge overhead, since these modules are singletons and only send one message over the bridge per event, regardless of the number of listeners, but it's still undesirable.
This fixes the problem by routing the `EmitterSubscription.remove()` method through the `EventEmitter` so that `NativeEventEmitter` can apply the additional native calls.
I've also improved the architecture so that each `NativeEventEmitter` uses its own `EventEmitter`, but they currently all still share the same `EventSubscriptionVendor` so that legacy code which registers events via `RCTDeviceEventEmitter` still works.
Reviewed By: vjeux
Differential Revision: D3292361
fbshipit-source-id: d60e881d50351523d2112473703bea826641cdef
Rahul Jiresal
Nick Lockwood