📅  最后修改于: 2022-03-11 14:48:16.032000             🧑  作者: Mango
/*You can use a BehaviorSubject for communicating between different
components throughout the app.
You can define a data sharing service containing the BehaviorSubject to
which you can subscribe and emit changes.
Define a data sharing service
*/
import { Injectable } from '@angular/core';
import { BehaviorSubject } from 'rxjs';
@Injectable()
export class DataSharingService {
public isUserLoggedIn: BehaviorSubject = new BehaviorSubject(false);
}
/*Add the DataSharingService in your AppModule providers entry.
Next, import the DataSharingService in your and in the
component where you perform the sign-in operation. In
subscribe to the changes to isUserLoggedIn subject:
*/
import { DataSharingService } from './data-sharing.service';
export class AppHeaderComponent {
// Define a variable to use for showing/hiding the Login button
isUserLoggedIn: boolean;
constructor(private dataSharingService: DataSharingService) {
// Subscribe here, this will automatically update
// "isUserLoggedIn" whenever a change to the subject is made.
this.dataSharingService.isUserLoggedIn.subscribe( value => {
this.isUserLoggedIn = value;
});
}
}
/*In your html template, you need to add the *ngIf
condition e.g.:
*/
// Finally, you just need to emit the event once the user has logged in e.g:
someMethodThatPerformsUserLogin() {
// Some code
// .....
// After the user has logged in, emit the behavior subject changes.
this.dataSharingService.isUserLoggedIn.next(true);
}