# All files / util async_observer.ts

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     /**
     * Copyright 2017 Google Inc.
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *   http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    import { Observer } from '../core/event_manager';
    import { EventHandler } from './misc';

    /*
     * A wrapper implementation of Observer<T> that will dispatch events
     * asynchronously. To allow immediate silencing, a mute call is added which
     * causes events scheduled to no longer be raised.
     */
    export class AsyncObserver<T> implements Observer<T> {
      /**
       * When set to true, will not raise future events. Necessary to deal with
       * async detachment of listener.
       */
      private muted = false;

      constructor(private observer: Observer<T>) {}

      next(value: T): void {
        this.scheduleEvent(this.observer.next, value);
      }

      error(error: Error): void {
        this.scheduleEvent(this.observer.error, error);
      }

      mute(): void {
        this.muted = true;
      }

      private scheduleEvent<E>(eventHandler: EventHandler<E>, event: E): void {
        Eif (!this.muted) {
          setTimeout(() => {
            Eif (!this.muted) {
              eventHandler(event);
            }
          }, 0);
        }
      }
    }