title: Chainig functions with observables fails to retrieve data
body: <p>Am performing one function after another has completed</p>
  
  <p>This is what i have tried</p>
  
  <pre><code>  ngOnInit () {
      this.subscriptions.add(
       this.route.params
        .subscribe(params =&gt; {
          this.truckdetails = params;
           this.getChecklistCategory();
         })
      )
   }
  
  
    getChecklistCategory(){
       this._checklistCategoryProvider.getAll()
          .subscribe(
             res=&gt;{
                  console.log("got data here") //this is never executed
                  ///this.checklists = res //this outputs data in frontend
                },
              err=&gt;{
                 console.log("error is here")//this is not executed
                }
           )
  
  
      }
  </code></pre>
  
  <p>The second function is never executed as check for both res and error</p>
  
  <p>Where am i going wrong?</p>