Can I catch certain errors before “subscribe()” in an RXJS observable in Angular2?

Question

Is it possible for a base class to catch certain errors before allowing the subclass to subscribe to the observable in Angular2.

e.g.

Answer 1

.catch() is the right one.

Observable is lazy, so there are no errors before you subscribe. Not sure if you mean this kind of "before" therefore I mention it just to be sure.

Answer 2

Using catch alone does not help much since you have client code subscribed and you must return Observable from catch.

I would implement it as follows:

Rx.Observable.of(42)
.do(v=>{throw new Error('test')})
.catch(Rx.Observable.of(undefined))
.filter(v=>{return v !== undefined})
.subscribe(
(e)=>{console.log('next', e)}, 
(e)=>{console.log('error', e)}, 
()=>{console.log('complete')}
);