Hedger Wang 6e2f07fb81 [Navigator] Add a callback that is called after emitting an event.
Summary:
While adeveloper requests the emitter to emit an event, the emitter
may not emit the event immediately instead of putting the request
into a queue and process it later.

This diff allows the developer to provide a callback which will be called
when the event has been emitted.

For instance:

```
class NavigationContext {
  push(nextRoute) {
    var nextStack = this._stack.push(nextRoute);
    this.emit(
      'change',
      {
        reason: 'push',
        nextStack: nextStack,
        nextRoute: nextRoute,
      },
      this._onPush
    );
  }

  _onPush(event){
    if (event.defaultPrevented) {
      return;
    }
    this._stack = event.nextStack;
    this.emit('change');
  }
}
```
2015-07-20 21:49:58 -08:00

86 lines
2.9 KiB
JavaScript

/**
* Copyright (c) 2015, Facebook, Inc. All rights reserved.
*
* Facebook, Inc. (“Facebook”) owns all right, title and interest, including
* all intellectual property and other proprietary rights, in and to the React
* Native CustomComponents software (the “Software”). Subject to your
* compliance with these terms, you are hereby granted a non-exclusive,
* worldwide, royalty-free copyright license to (1) use and copy the Software;
* and (2) reproduce and distribute the Software as part of your own software
* (“Your Software”). Facebook reserves all rights not expressly granted to
* you in this license agreement.
*
* THE SOFTWARE AND DOCUMENTATION, IF ANY, ARE PROVIDED "AS IS" AND ANY EXPRESS
* OR IMPLIED WARRANTIES (INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE) ARE DISCLAIMED.
* IN NO EVENT SHALL FACEBOOK OR ITS AFFILIATES, OFFICERS, DIRECTORS OR
* EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THE SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* @providesModule NavigationEventEmitter
* @flow
*/
'use strict';
var EventEmitter = require('EventEmitter');
var NavigationEvent = require('NavigationEvent');
type EventParams = {
data: any;
didEmitCallback: ?Function;
eventType: string;
};
class NavigationEventEmitter extends EventEmitter {
_emitQueue: Array<EventParams>;
_emitting: boolean;
_target: Object;
constructor(target: Object) {
super();
this._emitting = false;
this._emitQueue = [];
this._target = target;
}
emit(
eventType: string,
data: any,
didEmitCallback: ?Function
): void {
if (this._emitting) {
// An event cycle that was previously created hasn't finished yet.
// Put this event cycle into the queue and will finish them later.
this._emitQueue.push({eventType, data, didEmitCallback});
return;
}
this._emitting = true;
var event = new NavigationEvent(eventType, this._target, data);
// EventEmitter#emit only takes `eventType` as `String`. Casting `eventType`
// to `String` to make @flow happy.
super.emit(String(eventType), event);
if (typeof didEmitCallback === 'function') {
didEmitCallback.call(this._target, event);
}
event.dispose();
this._emitting = false;
while (this._emitQueue.length) {
var arg = this._emitQueue.shift();
this.emit(arg.eventType, arg.data, arg.didEmitCallback);
}
}
}
module.exports = NavigationEventEmitter;