Question

我创建了一项服务，以便从API中获取数据并使用主题从我的组件中获取这些数据（在应用程序初始化时调用LoadTenants）：

服务：

@Injectable()
 export class TenantService{
  public tenants;
  private tenantSubject = new Subject<any>();

constructor(private http: HttpClient) {
}

LoadTenants() {
    this.http.get(TENANT_URL).subscribe((data: any) => {
        this.tenants = data;
        this.setTenants();
    });
}

setTenants() {
    this.tenantSubject.next(this.tenants);
}

getTenants(): Observable<any> {
    return this.tenantSubject.asObservable();
}

getSyncTenants() {
    return this.tenants;
}
}

组件：

public tenant;
subsciption: Subscription;

constructor(private tenantService: TenantService) { }

ngOnInit() {
        this.subsciption = this.tenantService.getTenants().subscribe((datas) => {
            this.tenant = datas;
        },
            error => console.log('Error : ', error)
        );
    }
}

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

在第一次加载时一切运行正常，但是如果我导航到另一个组件并返回到该组件，则不会触发订阅，导致模板中的无效数据。

Answer 1

如果要获取最新值，请使用BehaviorSubject

BehaviorSubject将直接向订阅者发送当前值

 @Injectable()
     export class TenantService{
      public tenants;
      private tenantSubject = new BehaviorSubject<any>();

    constructor(private http: HttpClient) {
    }

    LoadTenants() {
        this.http.get(TENANT_URL).subscribe((data: any) => {
            this.tenants = data;
            this.setTenants();
        });
    }
    setTenants() {
      this.tenantSubject.next(this.tenants);
    }

   getTenants(): Observable<any> {
      return this.tenantSubject.asObservable();
   }

   getSyncTenants() {
      return this.tenants;
   }
  }

订阅仅触发一次的主题

1 个答案: