Angular's observables were unable to be subscribed to in either the constructor or ngOnInit() functions

Currently, I am incorporating an observable concept into my application. In this setup, a service is called by component1 to emit an event that is then subscribed to by component 2.

Below is the code snippet for reference:

Service Code


export class MessageService {
    private subject = new BehaviorSubject<any>("");
    message$ = this.subject.asObservable();
    
    sendMessage(message: string) { 
        console.log('sendMessage', message)
        this.subject.next({ text: message });

    }
    
    clearMessage() {
        this.subject.next("");
   }

Component1 Code

this.data.sendMessage('Printed');

Component2 Code

providers: [JsonDataService, MessageService]

constructor(public data?: MessageService) {}

ngOnInit() {
    this.data.message$.subscribe(res => { console.log('response', res); }, err => { console.log('error', err) });
}

While the sendMessage function successfully logs messages passed to it in the console, I am facing issues with receiving any responses or output from the subscription method defined in component2.

Answer №2

According to the official documentation, it is recommended that the service instance be shared by the components. I initially declared the service in both components, which caused issues with data emission from the service.

After moving the service declaration to the providers array in the app.module file, this issue was resolved.

A special thank you to @Vikas for providing the helpful hint.

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