title: Angular 2, can't get data after subscribe in ngOnInit
body: <p>I have a problem, maybe I don't understand how to do but when I try to catch data from an HttpRequest during angular ngOnInit, my console.log return me an "undefined" value. 
  The thing is that when I use this value in my template view it works !</p>
  
  <p>Here is my Component</p>
  
  <pre><code>export class ReferentielFormComponent implements OnInit {
    id: number;
    currentUser;
    referentiel;
    progressValue: number;
    formGroup: FormGroup;
    isNew: boolean;
  
    constructor(private service: AppService,
            private referentiels: ReferentielService,
            private router: ActivatedRoute,
            private config: NgbTabsetConfig) {
    }
  
    ngOnInit() {
      this.router.params.subscribe((params: Params) =&gt; this.id = params['id']);
      if (this.id) {
        this.referentiels.getReferentiel(this.id).subscribe(data =&gt; this.referentiel = data);
      } else {
        this.referentiel = {};
      }
      this.isNew = !this.referentiel;
  
      console.log(this.referentiel);
      console.log(this.isNew);
      this.progressValue = 20;
  
      this.formGroup = new FormGroup({
        titre: new FormControl(!this.isNew ? this.referentiel.titre : '', [
          Validators.required,
        ]),
        description: new FormControl(!this.isNew ? this.referentiel.description : '', [
          Validators.required,
        ])
      });
    }
  }
  </code></pre>
  
  <p>The variable this.referentiel return me an undefined so I can't bind my Form whith existing value because of that...</p>
  
  <p>Any suggestions ?</p>