具有可观察对象的Chainig函数无法检索数据

Question

执行一个又一个功能已完成

这就是我试过的

  ngOnInit () {
    this.subscriptions.add(
     this.route.params
      .subscribe(params => {
        this.truckdetails = params;
         this.getChecklistCategory();
       })
    )
 }


  getChecklistCategory(){
     this._checklistCategoryProvider.getAll()
        .subscribe(
           res=>{
                console.log("got data here") //this is never executed
                ///this.checklists = res //this outputs data in frontend
              },
            err=>{
               console.log("error is here")//this is not executed
              }
         )


    }

第二个函数永远不会执行检查res和错误

我哪里错了？