frompromise.md

Rx.Observable.fromPromise(promise)

Ⓢ

Converts a Promises/A+ spec compliant Promise and/or ES2015 compliant Promise or a factory function which returns said Promise to an Observable sequence.

Arguments

1. promise|Function: Promise - Promises/A+ spec compliant Promise to an Observable sequence or a function which returns a Promise.

Returns

Observable: An Observable sequence which wraps the existing promise success and failure.

Example

// Create a factory function which returns a promise
var promiseFn = function () { return Promise.resolve(42); };

var source = Rx.Observable.fromPromise(promiseFn);

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

// Create a promise which resolves 42
var promise1 = Promise.resolve(42)

var source1 = Rx.Observable.fromPromise(promise1);

var subscription1 = source1.subscribe(
  function (x) {
    console.log('Next: %s', x);
  },
  function (err) {
    console.log('Error: %s', err);
  },
  function () {
    console.log('Completed');
  });

// => Next: 42
// => Completed

// Create a promise which rejects with an error
var promise2 = Promise.reject(new Error('reason'));

var source2 = Rx.Observable.fromPromise(promise2);

var subscription2 = source2.subscribe(
  function (x) {
    console.log('Next: %s', x);
  },
  function (err) {
    console.log('Error: %s', err);
  },
  function () {
    console.log('Completed');
  });

// => Error: Error: reject

Location

File:

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

Dist:

• 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
• rx.lite.js | rx.lite.compat.js

NPM Packages:

• rx

NuGet Packages:

• RxJS-Async
• RxJS-Lite

Unit Tests:

• /tests/observable/frompromise.js