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Diffstat (limited to 'node_modules/rxjs/src/internal/observable/bindNodeCallback.ts')
| -rw-r--r-- | node_modules/rxjs/src/internal/observable/bindNodeCallback.ts | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/node_modules/rxjs/src/internal/observable/bindNodeCallback.ts b/node_modules/rxjs/src/internal/observable/bindNodeCallback.ts new file mode 100644 index 0000000..8d83722 --- /dev/null +++ b/node_modules/rxjs/src/internal/observable/bindNodeCallback.ts @@ -0,0 +1,131 @@ +/* @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); +} |
