79 lines
2.5 KiB
TypeScript
79 lines
2.5 KiB
TypeScript
// (C) Copyright 2015 Moodle Pty Ltd.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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import { EventEmitter } from '@angular/core';
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import { CoreUtils } from '@services/utils/utils';
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import { Observable, Subscription } from 'rxjs';
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/**
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* Subscribable object.
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*/
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type Subscribable<T> = EventEmitter<T> | Observable<T>;
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/**
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* Singleton with helpers to work with subscriptions.
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*/
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export class CoreSubscriptions {
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/**
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* Listen once to a subscribable object.
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*
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* @param subscribable Subscribable to listen to.
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* @param onSuccess Callback to run when the subscription is updated.
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* @param onError Callback to run when the an error happens.
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* @param onComplete Callback to run when the observable completes.
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* @returns A function to unsubscribe.
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*/
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static once<T>(
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subscribable: Subscribable<T>,
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onSuccess: (value: T) => unknown,
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onError?: (error: unknown) => unknown,
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onComplete?: () => void,
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): () => void {
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let callbackCalled = false;
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let subscription: Subscription | null = null;
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const runCallback = (callback) => {
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if (!callbackCalled) {
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callbackCalled = true;
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callback();
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}
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};
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const unsubscribe = async () => {
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// Subscription variable might not be set because we can receive a value immediately. Wait for next tick.
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await CoreUtils.nextTick();
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subscription?.unsubscribe();
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};
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subscription = subscribable.subscribe({
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next: value => {
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unsubscribe();
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runCallback(() => onSuccess(value));
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},
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error: error => {
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unsubscribe();
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runCallback(() => onError?.(error));
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},
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complete: () => {
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unsubscribe();
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runCallback(() => onComplete?.());
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},
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});
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return () => subscription?.unsubscribe();
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}
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}
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