主题值更改时不会触发订阅

Question

I have two components A and B, and when an event occurs in A, I need to get the updated value in B in which I am subscribing to a service to get the latest value from A.

component A:

sendString(inputEntered){  //happens when on buttonclick
....
this.myService.sendRecent(inputEntered);
}

Service:

export class myService {
  private inputStringSource = new Subject<string>();
  public inputString$ = this.inputStringSource.asObservable();
  constructor() {}


  sendRecent(inputString: string) {
    this.inputStringSource.next(inputString);
  }

component B:

...

  ngOnInit(): void {

    this.myService.inputString$.subscribe(data => {
      console.log("input value ", data);
    });

Service is receiving new value but the subscription in component B is not being triggered.. what am I doing wrong here? Please let me know. Tried few option but still no luck.

Answer 1

I think the problem might be with how you are importing service in your component. Now, since we don't have complete code reference, please make sure the module where you have put component B should not have service(myService in your example) in the providers list. BehaviourSubject subscribe works when the service is not explicitly mentioned in the providers of parent module.

Answer 2

如果您在订阅组件 B 之前从组件 A 发送数据，则可能会发生这种情况，您可以尝试使用 ReplaySubject

private inputStringSource = new ReplaySubject<string>();

Answer 3

Change this and try:

import { BehaviorSubject } from 'rxjs';

private inputStringSource = new BehaviorSubject<string>('');

If it doesn't works, try this change the service like this:

export class myService {

  private inputStringSource = new Subject<string>();

  public get inputString$() {
     return this.inputStringSource.asObservable();
  }
  
  constructor() {}


  sendRecent(inputString: string) {
    this.inputStringSource.next(inputString);
  }