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- /* @prettier */
- import { Observable } from '../Observable';
- import { SchedulerLike } from '../types';
- import { bindCallbackInternals } from './bindCallbackInternals';
- export function bindNodeCallback(
- callbackFunc: (...args: any[]) => void,
- resultSelector: (...args: any[]) => any,
- scheduler?: SchedulerLike
- ): (...args: any[]) => Observable<any>;
- // args is the arguments array and we push the callback on the rest tuple since the rest parameter must be last (only item) in a parameter list
- export function bindNodeCallback<A extends readonly unknown[], R extends readonly unknown[]>(
- callbackFunc: (...args: [...A, (err: any, ...res: R) => void]) => void,
- schedulerLike?: SchedulerLike
- ): (...arg: A) => Observable<R extends [] ? void : R extends [any] ? R[0] : R>;
- /**
- * 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.
- *
- * 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 `scheduler` provided as optional third parameter. {@link SchedulerLike}
- * can also control when values from callback will be emitted by Observable.
- * To find out more, check out documentation for {@link bindCallback}, where
- * {@link SchedulerLike} 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.
- *
- * ## Examples
- *
- * Read a file from the filesystem and get the data as an Observable
- *
- * ```ts
- * import * as fs from 'fs';
- * const readFileAsObservable = bindNodeCallback(fs.readFile);
- * const result = readFileAsObservable('./roadNames.txt', 'utf8');
- * result.subscribe(x => console.log(x), e => console.error(e));
- * ```
- *
- * Use on function calling callback with multiple arguments
- *
- * ```ts
- * someFunction((err, a, b) => {
- * console.log(err); // null
- * console.log(a); // 5
- * console.log(b); // "some string"
- * });
- * const boundSomeFunction = bindNodeCallback(someFunction);
- * boundSomeFunction()
- * .subscribe(value => {
- * console.log(value); // [5, "some string"]
- * });
- * ```
- *
- * Use on function calling callback in regular style
- *
- * ```ts
- * someFunction(a => {
- * console.log(a); // 5
- * });
- * const boundSomeFunction = bindNodeCallback(someFunction);
- * boundSomeFunction()
- * .subscribe(
- * value => {} // never gets called
- * err => console.log(err) // 5
- * );
- * ```
- *
- * @see {@link bindCallback}
- * @see {@link from}
- *
- * @param callbackFunc Function with a Node.js-style callback as the last parameter.
- * @param resultSelector A mapping function used to transform callback events.
- * @param scheduler The scheduler on which to schedule the callbacks.
- * @return A function which returns the Observable that delivers the same values the
- * Node.js callback would deliver.
- */
- export function bindNodeCallback(
- callbackFunc: (...args: [...any[], (err: any, ...res: any) => void]) => void,
- resultSelector?: ((...args: any[]) => any) | SchedulerLike,
- scheduler?: SchedulerLike
- ): (...args: any[]) => Observable<any> {
- return bindCallbackInternals(true, callbackFunc, resultSelector, scheduler);
- }
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