import { Operator } from '../Operator'; import { Subscriber } from '../Subscriber'; import { Observable } from '../Observable'; import { PartialObserver } from '../Observer'; import { TeardownLogic } from '../Subscription'; import { MonoTypeOperatorFunction } from '../interfaces'; /* tslint:disable:max-line-length */ export function tap(next: (x: T) => void, error?: (e: any) => void, complete?: () => void): MonoTypeOperatorFunction; export function tap(observer: PartialObserver): MonoTypeOperatorFunction; /* tslint:enable:max-line-length */ /** * Perform a side effect for every emission on the source Observable, but return * an Observable that is identical to the source. * * Intercepts each emission on the source and runs a * function, but returns an output which is identical to the source as long as errors don't occur. * * * * Returns a mirrored Observable of the source Observable, but modified so that * the provided Observer is called to perform a side effect for every value, * error, and completion emitted by the source. Any errors that are thrown in * the aforementioned Observer or handlers are safely sent down the error path * of the output Observable. * * This operator is useful for debugging your Observables for the correct values * or performing other side effects. * * Note: this is different to a `subscribe` on the Observable. If the Observable * returned by `do` is not subscribed, the side effects specified by the * Observer will never happen. `do` therefore simply spies on existing * execution, it does not trigger an execution to happen like `subscribe` does. * * @example Map every click to the clientX position of that click, while also logging the click event * var clicks = Rx.Observable.fromEvent(document, 'click'); * var positions = clicks * .do(ev => console.log(ev)) * .map(ev => ev.clientX); * positions.subscribe(x => console.log(x)); * * @see {@link map} * @see {@link subscribe} * * @param {Observer|function} [nextOrObserver] A normal Observer object or a * callback for `next`. * @param {function} [error] Callback for errors in the source. * @param {function} [complete] Callback for the completion of the source. * @return {Observable} An Observable identical to the source, but runs the * specified Observer or callback(s) for each item. * @name tap */ export function tap(nextOrObserver?: PartialObserver | ((x: T) => void), error?: (e: any) => void, complete?: () => void): MonoTypeOperatorFunction { return function tapOperatorFunction(source: Observable): Observable { return source.lift(new DoOperator(nextOrObserver, error, complete)); }; } class DoOperator implements Operator { constructor(private nextOrObserver?: PartialObserver | ((x: T) => void), private error?: (e: any) => void, private complete?: () => void) { } call(subscriber: Subscriber, source: any): TeardownLogic { return source.subscribe(new DoSubscriber(subscriber, this.nextOrObserver, this.error, this.complete)); } } /** * We need this JSDoc comment for affecting ESDoc. * @ignore * @extends {Ignored} */ class DoSubscriber extends Subscriber { private safeSubscriber: Subscriber; constructor(destination: Subscriber, nextOrObserver?: PartialObserver | ((x: T) => void), error?: (e: any) => void, complete?: () => void) { super(destination); const safeSubscriber = new Subscriber(nextOrObserver, error, complete); safeSubscriber.syncErrorThrowable = true; this.add(safeSubscriber); this.safeSubscriber = safeSubscriber; } protected _next(value: T): void { const { safeSubscriber } = this; safeSubscriber.next(value); if (safeSubscriber.syncErrorThrown) { this.destination.error(safeSubscriber.syncErrorValue); } else { this.destination.next(value); } } protected _error(err: any): void { const { safeSubscriber } = this; safeSubscriber.error(err); if (safeSubscriber.syncErrorThrown) { this.destination.error(safeSubscriber.syncErrorValue); } else { this.destination.error(err); } } protected _complete(): void { const { safeSubscriber } = this; safeSubscriber.complete(); if (safeSubscriber.syncErrorThrown) { this.destination.error(safeSubscriber.syncErrorValue); } else { this.destination.complete(); } } }