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feat(tap): add higher-order lettable version of do
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NOTE: Since `do` is an invalid function name, it's called `tap`, which comes from older versions of RxJS
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benlesh committed Jun 16, 2017
1 parent 408a2af commit f85c60e
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Showing 3 changed files with 126 additions and 66 deletions.
69 changes: 3 additions & 66 deletions src/operator/do.ts
Original file line number Diff line number Diff line change
@@ -1,8 +1,7 @@
import { Operator } from '../Operator';
import { Subscriber } from '../Subscriber';

import { Observable } from '../Observable';
import { PartialObserver } from '../Observer';
import { TeardownLogic } from '../Subscription';
import { tap as higherOrder } from '../operators';

/* tslint:disable:max-line-length */
export function _do<T>(this: Observable<T>, next: (x: T) => void, error?: (e: any) => void, complete?: () => void): Observable<T>;
Expand Down Expand Up @@ -55,67 +54,5 @@ export function _do<T>(this: Observable<T>, observer: PartialObserver<T>): Obser
export function _do<T>(this: Observable<T>, nextOrObserver?: PartialObserver<T> | ((x: T) => void),
error?: (e: any) => void,
complete?: () => void): Observable<T> {
return this.lift(new DoOperator(nextOrObserver, error, complete));
}

class DoOperator<T> implements Operator<T, T> {
constructor(private nextOrObserver?: PartialObserver<T> | ((x: T) => void),
private error?: (e: any) => void,
private complete?: () => void) {
}
call(subscriber: Subscriber<T>, 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<T> extends Subscriber<T> {

private safeSubscriber: Subscriber<T>;

constructor(destination: Subscriber<T>,
nextOrObserver?: PartialObserver<T> | ((x: T) => void),
error?: (e: any) => void,
complete?: () => void) {
super(destination);

const safeSubscriber = new Subscriber<T>(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();
}
}
return higherOrder(<any>nextOrObserver, error, complete)(this);
}
1 change: 1 addition & 0 deletions src/operators/index.ts
Original file line number Diff line number Diff line change
Expand Up @@ -12,3 +12,4 @@ export { reduce } from './reduce';
export { scan } from './scan';
export { switchMap } from './switchMap';
export { takeLast } from './takeLast';
export { tap } from './tap';
122 changes: 122 additions & 0 deletions src/operators/tap.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,122 @@
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<T>(next: (x: T) => void, error?: (e: any) => void, complete?: () => void): MonoTypeOperatorFunction<T>;
export function tap<T>(observer: PartialObserver<T>): MonoTypeOperatorFunction<T>;
/* 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.
*
* <span class="informal">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.</span>
*
* <img src="./img/do.png" width="100%">
*
* 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 <caption>Map every click to the clientX position of that click, while also logging the click event</caption>
* 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<T>(nextOrObserver?: PartialObserver<T> | ((x: T) => void),
error?: (e: any) => void,
complete?: () => void): MonoTypeOperatorFunction<T> {
return function tapOperatorFunction(source: Observable<T>): Observable<T> {
return source.lift(new DoOperator(nextOrObserver, error, complete));
};
}

class DoOperator<T> implements Operator<T, T> {
constructor(private nextOrObserver?: PartialObserver<T> | ((x: T) => void),
private error?: (e: any) => void,
private complete?: () => void) {
}
call(subscriber: Subscriber<T>, 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<T> extends Subscriber<T> {

private safeSubscriber: Subscriber<T>;

constructor(destination: Subscriber<T>,
nextOrObserver?: PartialObserver<T> | ((x: T) => void),
error?: (e: any) => void,
complete?: () => void) {
super(destination);

const safeSubscriber = new Subscriber<T>(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();
}
}
}

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