Angular服务未将数据分配给局部变量[重复]

Question

我正在尝试使用 GET 请求来接收要放入局部变量的数据。如果这在 subscibe 代码中，我已经能够获取局部变量以在控制台管理员中显示其数据。但是，当我将 console.log 放在外面时，它不起作用。为什么控制台中没有显示“this.taskSchedule”？

export class TestTaskComponent implements OnInit {
  profileForm: FormGroup;

  taskSchedule: any = {};


  constructor(
    private taskScheduleService: TaskScheduleService,
    private stateStorageService: StateStorageService,
    private router: Router) { }

  ngOnInit() {
    this.taskId = this.stateStorageService.getCurrentTaskId();

    this.taskScheduleService.getTaskSchedule(19).subscribe(data => {
      this.taskSchedule = data;
    });
    console.log(this.taskSchedule);
  }
}

在控制台输出中，它只是说“未定义”。 它应该输出 API 数据

Answer 1

因为您试图在异步订阅块之后访问它。通读我的 cmets。

ngOnInit() {
    // This is an asynchronous function
    this.taskScheduleService.getTaskSchedule(19).subscribe((data) => {
    // Here you can access this.taskSchedule
    this.taskSchedule = data;
    // Here we know that the value is assigned and we will call another method
    this.accessTaskSchedule();
    });
    // This is where the subscribe block ends so when you try to console this.taskSchedule you will find it empty or not yet assigned
    console.log(this.taskSchedule);
}

// let's have another method where we could access the local variable
accessTaskSchedule() {
    // here you would be able to access this because you made sure that you are using it after it's set
    console.log(this.taskSchedule);
}