why should we use subscribe() over map() in Angular?

Question

I am trying to take advantage of observables in angular2 and got confused on why should i use map() over subscribe(). Suppose i am getting values f

Answer 1

Observables are streams and they are designed to be written in functional streams. You should use RxJS operations because it is the 'functional' way of implementing subsctiptions to observables. Usually this happens when we take data outside of the Observable stream.

This is an asynchronous operation forced to work synchronously.

bad_example() {
  let id;
  this.obs.subscribe(param => id = param['id']);
    this.get(id).subscribe(elem => this.elem = elem);
}

This is an asynchronous operation that works as supposed to work. (As a stream)

good_example() {
  this.obs
    .map(param => param['id'])
    .switchMap(id => return this.get(id))
    .subscribe(elem => this.elem = elem);
}