How to Access the Current Value of an RxJS Subject or Observable?

Accessing the Current Value of an RxJS Subject or Observable

RxJS subjects and observables do not inherently hold a current value. When a value is emitted, it is only passed to subscribers momentarily.

However, in scenarios where a current value is crucial, consider utilizing BehaviorSubject, a specialized subject designed for this purpose. BehaviorSubject maintains the latest emitted value, providing it instantaneously to new subscribers and offering a getValue() method to retrieve the current value.

Example:

In our Angular service, let's replace Subject with BehaviorSubject:

<code class="typescript">private _isLoggedInSource = new BehaviorSubject<boolean>(false);
isLoggedIn = this._isLoggedInSource.asObservable();</code>

Now, we can access the current value using getValue():

<code class="typescript">import { SessionStorage } from './session-storage.service';
import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'my-component',
  templateUrl: './my-component.html'
})
export class MyComponent implements OnInit {

  isLoggedIn: boolean;

  constructor(private sessionStorage: SessionStorage) { }

  ngOnInit() {
    this.isLoggedIn = this.sessionStorage.isLoggedIn.getValue();
  }

}</code>

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