为什么在@ angular / redux-store中使用@select时，Angular Guard的行为会有所不同

Question

• I have an Angular setup that uses two guard. canLoad and canActivate
• both get fed with the same observable from the @angular-redux/store via @select

Question : Why does canActivate work with the observable that @select returns while canLoad breaks all routing from then on? What is the difference between the two guards?

Related angular issue: https://github.com/angular/angular/issues/18991

auth.guard.ts

@Injectable()
export class AuthGuard implements CanLoad, CanActivate {

  @select() readonly authenticated$: Observable<boolean>; // @angular-redux/store

  canLoad(): Observable<boolean> | boolean {
    // return true; // works
    return this.authenticated$; // ERROR: all routing stops from and to the current page
  }

  canActivate(): Observable<boolean> | boolean {
    // return true; // works
    return this.authenticated$; // works
  }

}

app-routing.module

const routes: Routes = [
  {
    path: '',
    component: SomeAComponent,
    pathMatch: 'full'
  },
  {
    path: 'someb',
    component: SomeBComponent,
    canActivate: [
      AuthGuard
    ],
  },
  {
    path: 'lazy',
    loadChildren: './lazy/lazy.module#LazyModule',
    canLoad: [
      AuthGuard
    ]
  },
  {
    path: '**',
    redirectTo: '/'
  }
];

Answer 1

The same issue I had, so to resolve it and let working in both CanLoad and CanActivate, you should add operator take(1)

@Injectable()
export class AuthGuard implements CanLoad, CanActivate {

  @select() readonly authenticated$: Observable<boolean>; // @angular-redux/store

  canLoad(): Observable<boolean> | boolean {
    // return true; // works
    return this.authenticated$.pipe(take(1));
  }

  canActivate(): Observable<boolean> | boolean {
    // return true; // works
    return this.authenticated$; 
  }

}

Answer 2

I just ran into the same issue and I do think that this is a bug in angular. I ended up just rewriting my guard to store a local variable that is populated by subscribing to the Observable. I am using ngrx/store here.

@Injectable()
export class MustBeAuthenticatedGuard implements CanActivate, CanLoad {

  constructor(private store: Store<fromAuth.State>) {
    store.select(fromAuth.authenticated)
      .subscribe((authenticated) => {
        this.authenticated = authenticated;
      });
  }

  private authenticated: boolean

  canLoad(): boolean {
    return this.isAuthenticated();
  }

  canActivate(): boolean {
    return this.isAuthenticated();
  }

  private isAuthenticated() {
    if (!this.authenticated) {
      this.store.dispatch(new SignIn());
    }
    return this.authenticated;
  }
}