title: Subscribe() returns undefined
body: <p>I'm not being able to use the result from subscribe() outside of subscribe(), console.log always returns undefined. My assumption is that it has something to do with the async thing but I don't know a workaround to make this work. Should I use promise instead?</p>
  
  <pre><code>export class MyComponent implements OnInit {
      textt: String;
  
      constructor(private tstService: MyComponentService) { this.source = new LocalDataSource(this.data) }
  
      ngOnInit(): void {
          this.tstService.getTstWithObservable()
          .map(result =&gt; result.map(i =&gt; i.user.data))
          .subscribe(
             res =&gt; { this.textt = res[0].title; }
         );
      }
  
      data = [
          {
            title: this.textt,
            sdate: '01/04/1990',
            edate: '30/09/1990',
          },
        ];
  
      source: LocalDataSource;
  }
  </code></pre>