Action on subscribe() and unsubscribe()

Question

in RxJS I'd like to take some special action once an Observer subscribes to an Observable and when he unsubscribes. I can of course overwrite the subscribe() and unsubscribe() methods, but that seems crud. Isn't there a way during creation of the observable to supply callbacks that get called whenever someone subscribes/unsubscribes? BR, Daniel

Answer 1

This is what Observable.create is for. You can create your own observable with specified attach/detach handlers, and can even wrap existing observables with just 2 additional lines of code.

const obs = Rx.Observable.create(observer => {
  console.log('attach');
  // If you want to wrap another observable, call this:
  // const subs = other.subscribe(observer);
  return () => {
    // subs.unsubscribe();
    console.log('detach');
  };
});

console.log('subscribe subscription1');
const subscribtion1 = obs.subscribe(() => {});
console.log('subscribe subscription2');
const subscribtion2 = obs.subscribe(() => {});
setTimeout(() => {
  console.log('subscribtion1.dispose()');
  subscribtion1.unsubscribe();
}, 500);
setTimeout(() => {
  console.log('subscribtion2.dispose()');
  subscribtion2.unsubscribe();
}, 1000);

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