问如何在另一个服务中使用AlertService (用于错误消息的快捷栏)？
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Stack Overflow用户

提问于 2018-08-27 14:07:13

回答 1查看 1.9K关注 0票数 3

我正在尝试订阅一个服务中的观察者。但是，我需要使用AlertService来显示错误。一个服务在另一个服务中(循环依赖？)。

这是AlertService

@Injectable()
export class AlertService {
  private subject = new Subject<any>();
  private keepAfterNavigationChange = false;

  constructor(private router: Router) {
    // clear alert message on route change
    router.events.subscribe(event => {
      if (event instanceof NavigationStart) {
        if (this.keepAfterNavigationChange) {
          // only keep for a single location change
          this.keepAfterNavigationChange = false;
        } else {
          // clear alert
          this.subject.next();
        }
      }
    });
  }

  success(message: string, keepAfterNavigationChange = false) {
    this.keepAfterNavigationChange = keepAfterNavigationChange;
    this.subject.next({ type: 'success', text: message });
  }

  error(message: string, keepAfterNavigationChange = false) {
    this.keepAfterNavigationChange = keepAfterNavigationChange;
    this.subject.next({ type: 'error', text: message });
  }

  getMessage(): Observable<any> {
    return this.subject.asObservable();
  }
}

AlertService成为AlertComponent上的Mat Snackbar。我要在另一个组件上渲染这个快餐栏。

export class AlertComponent implements OnInit {
  message: any;

  constructor(private alertService: AlertService, public snackBar: MatSnackBar) { }

  ngOnInit() {
    // trigger Snackbar after AlertService is called
    this.alertService.getMessage().subscribe(message => {
      if (message != null) {
        // there is a message to show, so change snackbar style to match the message type
        if (message.type === 'error') {
          this.snackBar.open(message.text, undefined, { duration: 8000, verticalPosition: 'bottom', panelClass: ['snackbar-error'] });
        } else if (message.type === 'success') {
          this.snackBar.open(message.text, undefined, { duration: 8000, verticalPosition: 'bottom', panelClass: ['snackbar-success'] });
        } else {
          this.snackBar.open(message.text, undefined, { duration: 8000, verticalPosition: 'bottom' });
        }
      }
    });
  }

}

我可以像这样订阅内部组件：

export class AboutComponent implements OnInit {
  
  ngOnInit() {
    this.emailService.sendEmail('example@gmail.com')
      .subscribe(code => {
          console.log(code);
          this.alertService.success('Thanks for your message!');
      }, error => {
        this.alertService.error('Error sending message.');
      }
    );
  }
      
}

@Injectable()
export class EmailService {

    constructor(private http: HttpClient) { }

    sendEmail(email: Email) {
        return this.http.post(BACKEND_URL + 'send', email);
    }
}

但是，我尝试在服务内部订阅，因为EmailService将在多个组件中使用。如何实现此行为？

angular

typescript

angular-material

回答 1

Stack Overflow用户

回答已采纳

发布于 2018-08-27 14:29:46

您的服务可以注入到其他服务中

@Injectable()export class EmailService {

constructor(private http: HttpClient, private alertService: AlertService) { }

sendEmail(email: Email) {
    return this.http.post(BACKEND_URL + 'send', email).map( result => this.alertService.alert(result););


  }
}