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### `Rx.Observable.using(resourceFactory, observableFactory)`
[Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/using.js "View in source")
Constructs an observable sequence that depends on a resource object, whose lifetime is tied to the resulting observable sequence's lifetime.
### Arguments
1. `resourceFactory` *(`Function`)*: Factory function to obtain a resource object.
2. `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
```js
/* 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
```
### Location
File:
- [`/src/core/linq/observable/using.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/using.js)
Dist:
- [`rx.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.js)
- [`rx.compat.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.compat.js)
Prerequisites:
- None
NPM Packages:
- [`rx`](https://www.npmjs.org/package/rx)
NuGet Packages:
- [`RxJS-Main`](http://www.nuget.org/packages/RxJS-Main/)
Unit Tests:
- [`/tests/observable/using.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/tests/observable/using.js)
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