es6/Subscriber.js

import { isFunction } from './util/isFunction';
import { Subscription } from './Subscription';
import { empty as emptyObserver } from './Observer';
import { rxSubscriber as rxSubscriberSymbol } from './symbol/rxSubscriber';
/**
 * 实现 {@link Observer} 接口并且继承 {@link Subscription} 类。
 * 虽然 {@link Observer} 是消费 {@link Observable} 值的公有 API, 所有 Observers 都转化成了
 * Subscriber，以便提供类似 Subscription 的能力，比如 `unsubscribe`。
 * Subscriber 是 RxJS 的常见类型, 并且是实现操作符的关键, 但是很少作为公有 API
 * 使用。
 *
 * @class Subscriber<T>
 */
export class Subscriber extends Subscription {
    /**
     * @param {Observer|function(value: T): void} [destinationOrNext] 部分定义的 Observer 或者 `next` 回调函数。
     * @param {function(e: ?any): void} [error] Observer 的 `error` 回调函数。
     * @param {function(): void} [complete] Observer 的 `complete` 回调函数。
     */
    constructor(destinationOrNext, error, complete) {
        super();
        this.syncErrorValue = null;
        this.syncErrorThrown = false;
        this.syncErrorThrowable = false;
        this.isStopped = false;
        switch (arguments.length) {
            case 0:
                this.destination = emptyObserver;
                break;
            case 1:
                if (!destinationOrNext) {
                    this.destination = emptyObserver;
                    break;
                }
                if (typeof destinationOrNext === 'object') {
                    if (destinationOrNext instanceof Subscriber) {
                        this.destination = destinationOrNext;
                        this.destination.add(this);
                    }
                    else {
                        this.syncErrorThrowable = true;
                        this.destination = new SafeSubscriber(this, destinationOrNext);
                    }
                    break;
                }
            default:
                this.syncErrorThrowable = true;
                this.destination = new SafeSubscriber(this, destinationOrNext, error, complete);
                break;
        }
    }
    [rxSubscriberSymbol]() { return this; }
    /**
     * Subscriber 的静态工厂，给定了 Observer （潜在的部分）的定义。
     * @param {function(x: ?T): void} [next] Observer 的 `next` 回调函数。
     * @param {function(e: ?any): void} [error] Observer 的 `error` 回调函数。
     * @param {function(): void} [complete] Observer 的 `complete` 回调函数。
     * @return {Subscriber<T>} 包装了作为参数传入的（部分定义）Observer 的  Subscriber。
     */
    static create(next, error, complete) {
        const subscriber = new Subscriber(next, error, complete);
        subscriber.syncErrorThrowable = false;
        return subscriber;
    }
    /**
     * {@link Observer} 的回调，用来接收 Observable 中的 next 类型通知，此通知带有值。
     * Observable 可能会掉用这个方法 0 次，或者多次。
     * @param {T} [value] The `next` value.
     * @return {void}
     */
    next(value) {
        if (!this.isStopped) {
            this._next(value);
        }
    }
    /**
     * {@link Observer} 的回调，用来接收 Observable 中的 error 类型通知，此通知带有 {@link Error} 。
     * 通知 Observer，Observable 发出了错误。
     * @param {any} [err] `error` 异常.
     * @return {void}
     */
    error(err) {
        if (!this.isStopped) {
            this.isStopped = true;
            this._error(err);
        }
    }
    /**
     * {@link Observer}  的回调，用来接收 Observable 中的 `complete` 类型通知。
     * 通知 Observer， Observable 完成了基于推送体系的通知。
     * @return {void}
     */
    complete() {
        if (!this.isStopped) {
            this.isStopped = true;
            this._complete();
        }
    }
    unsubscribe() {
        if (this.closed) {
            return;
        }
        this.isStopped = true;
        super.unsubscribe();
    }
    _next(value) {
        this.destination.next(value);
    }
    _error(err) {
        this.destination.error(err);
        this.unsubscribe();
    }
    _complete() {
        this.destination.complete();
        this.unsubscribe();
    }
    _unsubscribeAndRecycle() {
        const { _parent, _parents } = this;
        this._parent = null;
        this._parents = null;
        this.unsubscribe();
        this.closed = false;
        this.isStopped = false;
        this._parent = _parent;
        this._parents = _parents;
        return this;
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class SafeSubscriber extends Subscriber {
    constructor(_parentSubscriber, observerOrNext, error, complete) {
        super();
        this._parentSubscriber = _parentSubscriber;
        let next;
        let context = this;
        if (isFunction(observerOrNext)) {
            next = observerOrNext;
        }
        else if (observerOrNext) {
            next = observerOrNext.next;
            error = observerOrNext.error;
            complete = observerOrNext.complete;
            if (observerOrNext !== emptyObserver) {
                context = Object.create(observerOrNext);
                if (isFunction(context.unsubscribe)) {
                    this.add(context.unsubscribe.bind(context));
                }
                context.unsubscribe = this.unsubscribe.bind(this);
            }
        }
        this._context = context;
        this._next = next;
        this._error = error;
        this._complete = complete;
    }
    next(value) {
        if (!this.isStopped && this._next) {
            const { _parentSubscriber } = this;
            if (!_parentSubscriber.syncErrorThrowable) {
                this.__tryOrUnsub(this._next, value);
            }
            else if (this.__tryOrSetError(_parentSubscriber, this._next, value)) {
                this.unsubscribe();
            }
        }
    }
    error(err) {
        if (!this.isStopped) {
            const { _parentSubscriber } = this;
            if (this._error) {
                if (!_parentSubscriber.syncErrorThrowable) {
                    this.__tryOrUnsub(this._error, err);
                    this.unsubscribe();
                }
                else {
                    this.__tryOrSetError(_parentSubscriber, this._error, err);
                    this.unsubscribe();
                }
            }
            else if (!_parentSubscriber.syncErrorThrowable) {
                this.unsubscribe();
                throw err;
            }
            else {
                _parentSubscriber.syncErrorValue = err;
                _parentSubscriber.syncErrorThrown = true;
                this.unsubscribe();
            }
        }
    }
    complete() {
        if (!this.isStopped) {
            const { _parentSubscriber } = this;
            if (this._complete) {
                const wrappedComplete = () => this._complete.call(this._context);
                if (!_parentSubscriber.syncErrorThrowable) {
                    this.__tryOrUnsub(wrappedComplete);
                    this.unsubscribe();
                }
                else {
                    this.__tryOrSetError(_parentSubscriber, wrappedComplete);
                    this.unsubscribe();
                }
            }
            else {
                this.unsubscribe();
            }
        }
    }
    __tryOrUnsub(fn, value) {
        try {
            fn.call(this._context, value);
        }
        catch (err) {
            this.unsubscribe();
            throw err;
        }
    }
    __tryOrSetError(parent, fn, value) {
        try {
            fn.call(this._context, value);
        }
        catch (err) {
            parent.syncErrorValue = err;
            parent.syncErrorThrown = true;
            return true;
        }
        return false;
    }
    _unsubscribe() {
        const { _parentSubscriber } = this;
        this._context = null;
        this._parentSubscriber = null;
        _parentSubscriber.unsubscribe();
    }
}
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