从子组件更新UI的角度将值反映到父组件

Question

I, am using *IF-else statement in angular 5. If the authorization value is true the template 2 should render if not template 1 should render. Here is the code

<div *ngIf="authorized; then picUrl else login"></div>

                <ng-template #login>
                    <button mat-raised-button color="accent" class="mdl-cell mdl-cell--12-col mdl-color-text--white" style="background: #033342" (click)="openDialog()">Login</button>
                </ng-template>
                <ng-template #picUrl>
                    <img src="{{_loginVM.profilePic}}" class="img-thumbnail" alt="profile pic">
                </ng-template>

Calling the social component

<social></social>

App.component.ts

export class AppComponent {
    public authorized: boolean = false;
}

Social component.ts

import { AppComponent} from '../app/app.component'

    export class SocialComponent {
        private _appComponent: AppComponent;
        constructor(private socialAuthService: AuthService, appComponent: AppComponent,
            public dialogRef: MatDialogRef<SignInSignUpDialogHomeComponent>) {
            this._appComponent = appComponent;
        }
     public socialSignIn(socialPlatform: string) {
            let socialPlatformProvider: any;
            if (socialPlatform == "facebook") {
                socialPlatformProvider = FacebookLoginProvider.PROVIDER_ID;
            } else if (socialPlatform == "google") {
                socialPlatformProvider = GoogleLoginProvider.PROVIDER_ID;
            }

            this.socialAuthService.signIn(socialPlatformProvider).then(
                (userData) => {
                    if (userData != null) {
                        this._appComponent.authorized = true;
                        this._appComponent._loginVM.profilePic = userData.image;
                        this.dialogRef.close();
                    }
                }
            );
        }

After the successfully login the value is updated as this._appComponent.authorized = true; . The value is not reflected to the UI/UX.

I found some references from here https://angularfirebase.com/lessons/sharing-data-between-angular-components-four-methods/

I, tried with BehaviorSubject<boolean> . But no know how to subscribe to the UI data bind. Is, this is the way I, have to do?. Can't I do directly to the component variable?

Answer 1

.html

<div *ngIf="authorized; then picUrl else login"></div>

component.ts

ngOnInit() {
this.authorized= this.authService.isLoggedIn;
}

service.ts

get isLoggedIn(): boolean {
    return this.currentUser != null; //you can decide to return true or false
 }
get currentuser(): user{
  let user = localstorage.getitem('details')
return user;
}