node_modules/rxjs/_esm2015/observable/BoundCallbackObservable.js

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 BoundCallbackObservable extends Observable {
    constructor(callbackFunc, selector, args, context, scheduler) {
        super();
        this.callbackFunc = callbackFunc;
        this.selector = selector;
        this.args = args;
        this.context = context;
        this.scheduler = scheduler;
    }
    /* tslint:enable:max-line-length */
    /**
     * Converts a callback API to a function that returns an Observable.
     *
     * <span class="informal">Give it a function `f` of type `f(x, callback)` and
     * it will return a function `g` that when called as `g(x)` will output an
     * Observable.</span>
     *
     * `bindCallback` is not an operator because its input and output are not
     * Observables. The input is a function `func` with some parameters, the
     * last parameter must be a callback function that `func` calls when it is
     * done.
     *
     * The output of `bindCallback` 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. If function `func`
     * calls its callback with one argument the Observable will emit that value.
     * If on the other hand the callback is called with multiple values the resulting
     * Observable will emit an array with said values as arguments.
     *
     * It is very important to remember that input function `func` is not called
     * when the output function is, but rather when the Observable returned by the output
     * function is subscribed. This means if `func` makes an AJAX request, that request
     * will be made every time someone subscribes to the resulting Observable, but not before.
     *
     * Optionally, a selector function can be passed to `bindObservable`. The selector function
     * takes the same arguments as the callback and returns the value that will be emitted by the Observable.
     * Even though by default multiple arguments passed to callback appear in the stream as an array
     * the selector function will be called with arguments directly, just as the callback would.
     * This means you can imagine the default selector (when one is not provided explicitly)
     * as a function that aggregates all its arguments into an array, or simply returns first argument
     * if there is only one.
     *
     * The last optional parameter - {@link Scheduler} - can be used to control when the call
     * to `func` happens after someone subscribes to Observable, as well as when results
     * passed to callback will be emitted. By default, the subscription to  an Observable calls `func`
     * synchronously, but using `Scheduler.async` as the last parameter will defer the call to `func`,
     * just like wrapping the call in `setTimeout` with a timeout of `0` would. If you use the async Scheduler
     * and call `subscribe` on the output Observable all function calls that are currently executing
     * will end before `func` is invoked.
     *
     * By default results passed to the callback are emitted immediately after `func` invokes the callback.
     * In particular, if the callback is called synchronously the subscription of the resulting Observable
     * will call the `next` function synchronously as well.  If you want to defer that call,
     * you may use `Scheduler.async` just as before.  This means that by using `Scheduler.async` you can
     * ensure that `func` always calls its callback asynchronously, thus avoiding terrifying Zalgo.
     *
     * Note that the Observable created by the output function will always emit a single value
     * and then complete immediately. If `func` calls the callback multiple times, values from subsequent
     * calls will not appear in the stream. If you need to listen for multiple calls,
     *  you probably want to use {@link fromEvent} or {@link fromEventPattern} instead.
     *
     * If `func` depends on some context (`this` property) and is not already bound the context of `func`
     * will be the context that the output function has at call time. In particular, if `func`
     * is called as a method of some objec and if `func` is not already bound, in order to preserve the context
     * it is recommended that the context of the output function is set to that object as well.
     *
     * If the input function calls its callback in the "node style" (i.e. first argument to callback is
     * optional error parameter signaling whether the call failed or not), {@link bindNodeCallback}
     * provides convenient error handling and probably is a better choice.
     * `bindCallback` will treat such functions the same as any other and error parameters
     * (whether passed or not) will always be interpreted as regular callback argument.
     *
     *
     * @example <caption>Convert jQuery's getJSON to an Observable API</caption>
     * // Suppose we have jQuery.getJSON('/my/url', callback)
     * var getJSONAsObservable = Rx.Observable.bindCallback(jQuery.getJSON);
     * var result = getJSONAsObservable('/my/url');
     * result.subscribe(x => console.log(x), e => console.error(e));
     *
     *
     * @example <caption>Receive an array of arguments passed to a callback</caption>
     * someFunction((a, b, c) => {
     *   console.log(a); // 5
     *   console.log(b); // 'some string'
     *   console.log(c); // {someProperty: 'someValue'}
     * });
     *
     * const boundSomeFunction = Rx.Observable.bindCallback(someFunction);
     * boundSomeFunction().subscribe(values => {
     *   console.log(values) // [5, 'some string', {someProperty: 'someValue'}]
     * });
     *
     *
     * @example <caption>Use bindCallback with a selector function</caption>
     * someFunction((a, b, c) => {
     *   console.log(a); // 'a'
     *   console.log(b); // 'b'
     *   console.log(c); // 'c'
     * });
     *
     * const boundSomeFunction = Rx.Observable.bindCallback(someFunction, (a, b, c) => a + b + c);
     * boundSomeFunction().subscribe(value => {
     *   console.log(value) // 'abc'
     * });
     *
     *
     * @example <caption>Compare behaviour with and without async Scheduler</caption>
     * function iCallMyCallbackSynchronously(cb) {
     *   cb();
     * }
     *
     * const boundSyncFn = Rx.Observable.bindCallback(iCallMyCallbackSynchronously);
     * const boundAsyncFn = Rx.Observable.bindCallback(iCallMyCallbackSynchronously, null, Rx.Scheduler.async);
     *
     * boundSyncFn().subscribe(() => console.log('I was sync!'));
     * boundAsyncFn().subscribe(() => console.log('I was async!'));
     * console.log('This happened...');
     *
     * // Logs:
     * // I was sync!
     * // This happened...
     * // I was async!
     *
     *
     * @example <caption>Use bindCallback on an object method</caption>
     * const boundMethod = Rx.Observable.bindCallback(someObject.methodWithCallback);
     * boundMethod.call(someObject) // make sure methodWithCallback has access to someObject
     * .subscribe(subscriber);
     *
     *
     * @see {@link bindNodeCallback}
     * @see {@link from}
     * @see {@link fromPromise}
     *
     * @param {function} func A function with a callback as the last parameter.
     * @param {function} [selector] A function which takes the arguments from the
     * callback and maps them to a value that is emitted 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 callback would deliver.
     * @static true
     * @name bindCallback
     * @owner Observable
     */
    static create(func, selector = undefined, scheduler) {
        return function (...args) {
            return new BoundCallbackObservable(func, selector, args, this, 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;
                    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.context, args.concat(handler));
                if (result === errorObject) {
                    subject.error(errorObject.e);
                }
            }
            return subject.subscribe(subscriber);
        }
        else {
            return scheduler.schedule(BoundCallbackObservable.dispatch, 0, { source: this, subscriber, context: this.context });
        }
    }
    static dispatch(state) {
        const self = this;
        const { source, subscriber, context } = 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;
                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(context, 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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