Question

我有一个消息服务，可以在各个组件之间进行交互。当我单击Mine按钮时，我只想触发一条消息。到目前为止，该方法有效。但是，当我单击<和>按钮时，它会触发getMessage()，因此它会累加值。但是，我只想在单击Mine时发送一个值。仅最后一个值。在单击getMessage()和<时如何防止触发>？

当我点击<和>时，它会在1到10张卡之间切换。当我点击Mine时，它应该只拿走我正在使用的卡并发送从该块到另一个组件的信息。但是，相反，当我单击<或>时，getMessage()被呼叫，它将累加所有卡，直到我单击Mine。我该如何预防？

遵循一些代码。我试图使其紧凑：

Message-service.ts：

@Injectable({ providedIn: 'root' })
export class MessageService {
  private subject = new Subject<any>();

  sendMessage(message: string) {
    this.subject.next({ text: message });
  }

  getMessage(): Observable<any> {
    console.log('Get Message Message Service');
    return this.subject.asObservable();
  }

矿工卡组件：

  message: any;
  subscription: Subscription;

  constructor(private ref: ChangeDetectorRef, private emitTransactionService: EmitTransactionService,
              private messageService: MessageService) {
    this.subscription = this.messageService.getMessage().subscribe(message => {
      console.log('Constructor miner-card'); // gets called multiple times, depending on how often I click < and >. When I click 10 times on < or > it will call this subscription 10 times.
    });
  }

当我单击<和>时，这些函数被调用：根据minerCounter的值，将显示卡1-10。

  precedingBlock() {
    this.minerCounter--;

    if (this.minerCounter < 1) {
      this.minerCounter = 10;
    }
  }

  nextBlock() {
    this.minerCounter++;

    if (this.minerCounter > 10) {
      this.minerCounter = 1;
    }
  }

通过<和>按钮，卡片的外观如何：

Mine按钮：

Answer 1

您应始终unsubscribe ngOnDestroy中的订阅。

  message: any;
  subscription: Subscription;

  constructor(private ref: ChangeDetectorRef, private emitTransactionService: EmitTransactionService,
              private messageService: MessageService) {
    this.subscription = this.messageService.getMessage().subscribe(message => {
      console.log('Constructor miner-card'); // gets called multiple times, depending on how often I click < and >. When I click 10 times on < or > it will call this subscription 10 times.
    });
  }

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

Answer 2

检查您的订阅是否未定义。如果未定义，则仅订阅。

constructor(
private ref: ChangeDetectorRef,
private emitTransactionService: EmitTransactionService,
private messageService: MessageService
) {
if (!this.subscription) {
    this.subscription = this.messageService.getMessage().subscribe(message => {
      console.log('Constructor miner-card'); // gets called multiple times, depending on how often I click < and >. When I click 10 times on < or > it will call this subscription 10 times.
    });
  }
}

Answer 3

在您的miner-card.component.ts文件中，使用take(1)。这样只会从订阅中获取单个数据。

  message: any;
  subscription: Subscription;

  constructor(private ref: ChangeDetectorRef, private emitTransactionService: EmitTransactionService,
              private messageService: MessageService) {
    this.subscription = this.messageService.getMessage().pipe(take(1)).subscribe(message => {
      console.log('Constructor miner-card'); // gets called multiple times, depending on how often I click < and >. When I click 10 times on < or > it will call this subscription 10 times.
    });
  }

希望这会有所帮助！

如何防止在Angular中进行多个订阅调用？

3 个答案: