node_modules/rxjs/_esm2015/observable/BoundNodeCallbackObservable.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 BoundNodeCallbackObservable 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 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 object, signaling
     * whether call was successful. If that object is passed to callback, it means
     * something went wrong.
     *
     * 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.
     * If `func` calls its callback with error parameter present, Observable will
     * error with that value as well. If error parameter is not passed, Observable will emit
     * second parameter. If there are more parameters (third and so on),
     * Observable will emit an array with all arguments, except first error argument.
     *
     * Optionally `bindNodeCallback` accepts selector function, which allows you to
     * make resulting Observable emit value computed by selector, instead of regular
     * callback arguments. It works similarly to {@link bindCallback} selector, but
     * Node.js-style error argument will never be passed to that function.
     *
     * Note that `func` will not be called at the same time output function is,
     * but rather whenever resulting Observable is subscribed. By default call to
     * `func` will happen synchronously after subscription, but that can be changed
     * with proper {@link Scheduler} provided as optional third parameter. Scheduler
     * can also control when values from callback will be emitted by Observable.
     * To find out more, check out documentation for {@link bindCallback}, where
     * Scheduler works exactly the same.
     *
     * As in {@link bindCallback}, context (`this` property) of input function will be set to context
     * of returned function, when it is called.
     *
     * After Observable emits value, it will complete immediately. This means
     * even if `func` calls callback again, values from second and consecutive
     * calls will never appear on the stream. If you need to handle functions
     * that call callbacks multiple times, check out {@link fromEvent} or
     * {@link fromEventPattern} instead.
     *
     * Note that `bindNodeCallback` can be used in non-Node.js environments as well.
     * "Node.js-style" callbacks are just a convention, so if you write for
     * browsers or any other environment and API you use implements that callback style,
     * `bindNodeCallback` can be safely used on that API functions as well.
     *
     * Remember that Error object passed to callback does not have to be an instance
     * of JavaScript built-in `Error` object. In fact, it does not even have to an object.
     * Error parameter of callback function is interpreted as "present", when value
     * of that parameter is truthy. It could be, for example, non-zero number, non-empty
     * string or boolean `true`. In all of these cases resulting Observable would error
     * with that value. This means usually regular style callbacks will fail very often when
     * `bindNodeCallback` is used. If your Observable errors much more often then you
     * would expect, check if callback really is called in Node.js-style and, if not,
     * switch to {@link bindCallback} instead.
     *
     * Note that even if error parameter is technically present in callback, but its value
     * is falsy, it still won't appear in array emitted by Observable or in selector function.
     *
     *
     * @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));
     *
     *
     * @example <caption>Use on function calling callback with multiple arguments</caption>
     * someFunction((err, a, b) => {
     *   console.log(err); // null
     *   console.log(a); // 5
     *   console.log(b); // "some string"
     * });
     * var boundSomeFunction = Rx.Observable.bindNodeCallback(someFunction);
     * boundSomeFunction()
     * .subscribe(value => {
     *   console.log(value); // [5, "some string"]
     * });
     *
     *
     * @example <caption>Use with selector function</caption>
     * someFunction((err, a, b) => {
     *   console.log(err); // undefined
     *   console.log(a); // "abc"
     *   console.log(b); // "DEF"
     * });
     * var boundSomeFunction = Rx.Observable.bindNodeCallback(someFunction, (a, b) => a + b);
     * boundSomeFunction()
     * .subscribe(value => {
     *   console.log(value); // "abcDEF"
     * });
     *
     *
     * @example <caption>Use on function calling callback in regular style</caption>
     * someFunction(a => {
     *   console.log(a); // 5
     * });
     * var boundSomeFunction = Rx.Observable.bindNodeCallback(someFunction);
     * boundSomeFunction()
     * .subscribe(
     *   value => {}             // never gets called
     *   err => console.log(err) // 5
     *);
     *
     *
     * @see {@link bindCallback}
     * @see {@link from}
     * @see {@link fromPromise}
     *
     * @param {function} func Function with a Node.js-style callback as the last parameter.
     * @param {function} [selector] A function which takes the arguments from the
     * callback and maps those to 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 function (...args) {
            return new BoundNodeCallbackObservable(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;
                    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.context, args.concat(handler));
                if (result === errorObject) {
                    subject.error(errorObject.e);
                }
            }
            return subject.subscribe(subscriber);
        }
        else {
            return scheduler.schedule(dispatch, 0, { source: this, subscriber, context: this.context });
        }
    }
}
function dispatch(state) {
    const self = this;
    const { source, subscriber, context } = state;
    // XXX: cast to `any` to access to the private field in `source`.
    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) {
                self.add(scheduler.schedule(dispatchError, 0, { err, subject }));
            }
            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(context, args.concat(handler));
        if (result === errorObject) {
            self.add(scheduler.schedule(dispatchError, 0, { err: errorObject.e, subject }));
        }
    }
    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);
}
//# sourceMappingURL=BoundNodeCallbackObservable.js.map