Angular2 - How to chain async service calls (http requests) in a component?

Question

I have a component which first need to call a service that POST something. Then in the same component I want to wait until the POST is done, to call another service which

Answer 1

You should be able to concat to achieve sequence, and reduce to collect the emitted values:

var a = this._newVersionService.createNewVersion(vnr);
var b = this._versionService.getAvailableVersions(); 

Rx.Observable.concat(a, b).reduce((acc:Array, x:any) => {
    acc.push(x); return acc;
}, []).subscribe(t=> { 
      var firstEmitted = t[0];
      var secondEmitted = t[1];
});