fromcallback.md

Rx.Observable.fromCallback(func, [context], [selector])

Ⓢ

Converts a callback function to an observable sequence.

Arguments

1. func (Function): Function with a callback as the last parameter to convert to an Observable sequence.
2. [context] (Any): The context for the func parameter to be executed. If not specified, defaults to undefined.
3. [selector] (Function): A selector which takes the arguments from the callback to produce a single item to yield on next.

Returns

(Function): A function, when executed with the required parameters minus the callback, produces an Observable sequence with a single value of the arguments to the callback as an array if no selector given, else the object created by the selector function.

Example

var fs = require('fs'),
    Rx = require('rx');

// Wrap fs.exists
var exists = Rx.Observable.fromCallback(fs.exists);

// Check if file.txt exists
var source = exists('file.txt');

var subscription = source.subscribe(
    function (x) {
        console.log('Next: ' + x);
    },
    function (err) {
        console.log('Error: ' + err);
    },
    function () {
        console.log('Completed');
    });

// => Next: true
// => Completed

Location

File:

• /src/core/perf/operators/fromcallback.js

Dist:

• rx.all.js
• rx.all.compat.js
• rx.async.js
• rx.async.compat.js
• rx.lite.js
• rx.lite.compat.js

Prerequisites:

• If using rx.async.js | rx.async.compat.js
  • rx.js | rx.compat.js
  • rx.binding.js

NPM Packages:

• rx

NuGet Packages:

• RxJS-Complete
• RxJS-Async
• RxJS-Lite

Unit Tests:

• /tests/observable/fromcallback.js