Angular 2.x观察变量变化

您可能希望实现该OnChanges接口并实现该ngOnChanges()方法.只要其中一个组件输入或输出绑定值发生更改,就会调用此方法.另请参见https://angular.io/docs/ts/latest/guide/lifecycle-hooks.html

飞镖代码示例

  @Input() bool fixed;

  @override
  void ngOnChanges(Map changes) {
    print(changes);
  }

你可能会发现这个回答是委托:Angular2中的EventEmitter或Observable很有用(为我工作).

基本上你可以使用a BehaviorSubject,它允许你为你感兴趣的属性设置初始值,然后在注入服务的任何地方订阅对该属性的更改.

例如,如果我正确理解你,就像这样:

export class SomeService {
  private fixed = new BehaviorSubject(true); // true is your initial value
  fixed$ = this.fixed.asObservable();

  private set isFixed(value: boolean) {
    this.fixed.next(value);
    console.log('isFixed changed', value);
  }

  private get isFixed():boolean {
    return this.fixed.getValue()
  }

  constructor(router: Router, location: Location) {
    this.router = router;
    this.location = location;
  }
}

export class ObservingComponent {
  isFixed: boolean;
  subscription: Subscription;

  constructor(private someService: SomeService) {}

  ngOnInit() {
    this.subscription = this.someService.fixed$
      .subscribe(fixed => this.isFixed = fixed)
  }

  ngOnDestroy() {
    this.subscription.unsubscribe();
  }
}

export class Navigation {
  constructor(private someService: SomeService) {}

  selectedNavItem(item: number) {
    this.someService.isFixed(true);
  }
}