@reactivex/rxjs
Version:
Reactive Extensions for modern JavaScript
153 lines • 6.31 kB
JavaScript
import { Observable } from '../Observable';
import { tryCatch } from '../util/tryCatch';
import { errorObject } from '../util/errorObject';
import { AsyncSubject } from '../AsyncSubject';
/**
* We need this JSDoc comment for affecting ESDoc.
* @extends {Ignored}
* @hide true
*/
export class BoundNodeCallbackObservable extends Observable {
constructor(callbackFunc, selector, args, scheduler) {
super();
this.callbackFunc = callbackFunc;
this.selector = selector;
this.args = args;
this.scheduler = scheduler;
}
/* tslint:enable:max-line-length */
/**
* Converts a Node.js-style callback API to a function that returns an
* Observable.
*
* <span class="informal">It's just like {@link bindCallback}, but the
* callback is expected to be of type `callback(error, result)`.</span>
*
* `bindNodeCallback` is not an operator because its input and output are not
* Observables. The input is a function `func` with some parameters, but the
* last parameter must be a callback function that `func` calls when it is
* done. The callback function is expected to follow Node.js conventions,
* where the first argument to the callback is an error, while remaining
* arguments are the callback result. The output of `bindNodeCallback` is a
* function that takes the same parameters as `func`, except the last one (the
* callback). When the output function is called with arguments, it will
* return an Observable where the results will be delivered to.
*
* @example <caption>Read a file from the filesystem and get the data as an Observable</caption>
* import * as fs from 'fs';
* var readFileAsObservable = Rx.Observable.bindNodeCallback(fs.readFile);
* var result = readFileAsObservable('./roadNames.txt', 'utf8');
* result.subscribe(x => console.log(x), e => console.error(e));
*
* @see {@link bindCallback}
* @see {@link from}
* @see {@link fromPromise}
*
* @param {function} func Function with a callback as the last parameter.
* @param {function} selector A function which takes the arguments from the
* callback and maps those a value to emit on the output Observable.
* @param {Scheduler} [scheduler] The scheduler on which to schedule the
* callbacks.
* @return {function(...params: *): Observable} A function which returns the
* Observable that delivers the same values the Node.js callback would
* deliver.
* @static true
* @name bindNodeCallback
* @owner Observable
*/
static create(func, selector = undefined, scheduler) {
return (...args) => {
return new BoundNodeCallbackObservable(func, selector, args, scheduler);
};
}
_subscribe(subscriber) {
const callbackFunc = this.callbackFunc;
const args = this.args;
const scheduler = this.scheduler;
let subject = this.subject;
if (!scheduler) {
if (!subject) {
subject = this.subject = new AsyncSubject();
const handler = function handlerFn(...innerArgs) {
const source = handlerFn.source;
const { selector, subject } = source;
const err = innerArgs.shift();
if (err) {
subject.error(err);
}
else if (selector) {
const result = tryCatch(selector).apply(this, innerArgs);
if (result === errorObject) {
subject.error(errorObject.e);
}
else {
subject.next(result);
subject.complete();
}
}
else {
subject.next(innerArgs.length === 1 ? innerArgs[0] : innerArgs);
subject.complete();
}
};
// use named function instance to avoid closure.
handler.source = this;
const result = tryCatch(callbackFunc).apply(this, args.concat(handler));
if (result === errorObject) {
subject.error(errorObject.e);
}
}
return subject.subscribe(subscriber);
}
else {
return scheduler.schedule(dispatch, 0, { source: this, subscriber });
}
}
}
function dispatch(state) {
const self = this;
const { source, subscriber } = state;
const { callbackFunc, args, scheduler } = source;
let subject = source.subject;
if (!subject) {
subject = source.subject = new AsyncSubject();
const handler = function handlerFn(...innerArgs) {
const source = handlerFn.source;
const { selector, subject } = source;
const err = innerArgs.shift();
if (err) {
subject.error(err);
}
else if (selector) {
const result = tryCatch(selector).apply(this, innerArgs);
if (result === errorObject) {
self.add(scheduler.schedule(dispatchError, 0, { err: errorObject.e, subject }));
}
else {
self.add(scheduler.schedule(dispatchNext, 0, { value: result, subject }));
}
}
else {
const value = innerArgs.length === 1 ? innerArgs[0] : innerArgs;
self.add(scheduler.schedule(dispatchNext, 0, { value, subject }));
}
};
// use named function to pass values in without closure
handler.source = source;
const result = tryCatch(callbackFunc).apply(this, args.concat(handler));
if (result === errorObject) {
subject.error(errorObject.e);
}
}
self.add(subject.subscribe(subscriber));
}
function dispatchNext(arg) {
const { value, subject } = arg;
subject.next(value);
subject.complete();
}
function dispatchError(arg) {
const { err, subject } = arg;
subject.error(err);
}
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