`Rx.Observable.using(resourceFactory, observableFactory)`

Ⓢ

Constructs an observable sequence that depends on a resource object, whose lifetime is tied to the resulting observable sequence's lifetime.

Arguments

resourceFactory (Function): Factory function to obtain a resource object.
observableFactory (Function): Factory function to obtain an observable sequence that depends on the obtained resource.

Returns

(Function): An observable sequence whose lifetime controls the lifetime of the dependent resource object.

Example

/* Using an AsyncSubject as a resource which supports the .dispose method */
function DisposableResource(value) {
  this.value = value;
  this.disposed = false;
}

DisposableResource.prototype.getValue = function () {
  if (this.disposed) {
    throw new Error('Object is disposed');
  }
  return this.value;
};

DisposableResource.prototype.dispose = function () {
  if (!this.disposed) {
    this.disposed = true;
    this.value = null;
  }
  console.log('Disposed');
};

var source = Rx.Observable.using(
  function () { return new DisposableResource(42); },
  function (resource) {
    var subject = new Rx.AsyncSubject();
    subject.onNext(resource.getValue());
    subject.onCompleted();
    return subject;
  }
);

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

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

subscription.dispose();

// => Disposed