What is the cleanest way to perform a side-effect when the last subscription for a RxJS Observable is disposed? This may occur before the Observable has terminated.
Let's say that I need a function returning an Observable that emits changes to a resource. I'd like to perform a cleanup action when all subscriptions have been disposed.
var observable = streamResourceChanges(resource);
var subscription1 = observable.subscribe(observer1);
var subscription2 = observable.subscribe(observer2);
// ...
subscription1.dispose(); // Does not perform the cleanup
subscription2.dispose(); // Performs the cleanup
The only way I've found to define a subscription disposal action is to use Rx.Observable.create. The last disposal can be handled by sharing a subscription, for example with Observable.prototype.singleInstance().
For example:
function streamResourceChanges(resource) {
return Rx.Observable.create(function(observer) {
// Subscribe the observer for resource changes...
// Return a cleanup function
return function() {
// Perform cleanup here...
console.log("Cleanup performed!");
};
}).singleInstance();
}
Is there a neater way to define a side-effect for subscription disposal, similar to doOnNext, doOnCompleted or doOnError?
var withCleanup = withoutCleanup.doOnDispose(function() {
// Perform cleanup here...
});
What is the cleanest way to perform a side-effect when the last subscription for a RxJS Observable is disposed? This may occur before the Observable has terminated.
Let's say that I need a function returning an Observable that emits changes to a resource. I'd like to perform a cleanup action when all subscriptions have been disposed.
var observable = streamResourceChanges(resource);
var subscription1 = observable.subscribe(observer1);
var subscription2 = observable.subscribe(observer2);
// ...
subscription1.dispose(); // Does not perform the cleanup
subscription2.dispose(); // Performs the cleanup
The only way I've found to define a subscription disposal action is to use Rx.Observable.create. The last disposal can be handled by sharing a subscription, for example with Observable.prototype.singleInstance().
For example:
function streamResourceChanges(resource) {
return Rx.Observable.create(function(observer) {
// Subscribe the observer for resource changes...
// Return a cleanup function
return function() {
// Perform cleanup here...
console.log("Cleanup performed!");
};
}).singleInstance();
}
Is there a neater way to define a side-effect for subscription disposal, similar to doOnNext, doOnCompleted or doOnError?
var withCleanup = withoutCleanup.doOnDispose(function() {
// Perform cleanup here...
});
1 Answer
Reset to default 14Two choices e to mind depending upon your actual use case:
.finally()
source.finally(() => console.log("cleaning up")).singleInstance()
.using()
Rx.Observable
.using(
// allocate some disposable resource during subscribe.
// resource.dispose() will be called during unsubscribe.
() => new SomeResource(),
// use the disposable resource to create your observable
// for example...
resource => Rx.Observable.interval(resource.time))
.singleInstance();