Conditionally load module on the empty path in Angular router

Question

I'm trying to load the home page of my app for visitors who are not authenticated.

const routes: Routes = [
    { path: '', loadChildren: './home/home.module#HomeModule' }
...

Authenticated users should get their feed via that module, also on the empty path.

{ path: '', loadChildren: './feed/feed.module#FeedModule', canActivate: [IsAuthenticationGuard] },
{ path: '', loadChildren: './home/home.module#HomeModule', canActivate: [NoAuthenticationGuard] },

I would expect that IsAuthenticationGuard would fail and load the default home component.

Instead it DOES download the feed module package (shown in the network tab) but loads nothing in the router outlet. Very confusing.

How can I do conditional routing (based on guards or otherwise) on the empty path?

Update: Here are the guards by request

@Injectable()
export class IsAuthenticationGuard implements CanActivate {
    constructor(
        private authenticationService: AuthenticationService
    ) { }

    public canActivate(
        route: ActivatedRouteSnapshot,
        state: RouterStateSnapshot
    ): Observable<boolean> {
        return this.authenticationService.isAuthenticated.pipe(take(1), map((isAuthentication) => {
            return isAuthentication;
        }));
    }
}

I've researched the new urlTree and it's cool that you can now redirect via the route instead of within the guard. However, redirects don't seem applicable if you're trying to use the same route with a different module. Plz correct me if there is a way.

You needd to use matchers. check this for the clues: medium.com/@lenseg1/… — nircraft
– nircraft, Commented Dec 26, 2018 at 21:03
you can't put two empty paths, you should put one empty and give the other a url, then in the guards, you can do redirects by router.navigate — IT Warrior
– IT Warrior, Commented Jan 9, 2019 at 10:06
Although this feature does not exists there is a feature request at: github.com/angular/angular/issues/12088 — Top-Master
– Top-Master, Commented Feb 7, 2019 at 11:08
SOLUTION: You can do it with creating route matcher. CODE: I answered that here: stackoverflow.com/a/67422797/14389830 NOTE: In the linked answer there is a working example and linked relevant blogs for in-depth details and walk-through how to do it. — NeNaD
– NeNaD, Commented May 7, 2021 at 5:59

bodorgergely · Accepted Answer · 2018-12-27 09:35:27Z

3

There are a couple things that you are doing wrong in my opinion.

You shouldn't have two routes defined with the same path.
In your guard the map is pointless. As long as your service method returns Observable<boolean> you don't need to map its value.
Also in your guard if you're not returning true, you need to navigate to the other module's path. For that you will need to implement some other logic for telling whether the user is logged in or not.

Take a look at the official angular routing guide here. There is a lot of useful information that will help you. Especially these:

EDIT 2018/12/27

So if the question is how to conditionally load two feature modules on the same path,

the answer is, in my experience, you cannot.

edited Dec 27, 2018 at 9:35

answered Dec 26, 2018 at 23:46

bodorgergely

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4 Comments

Ben Racicot Over a year ago

Thanks bodogergely for the answer! But I know how to do all of that. Also redirects aren't applicable. The question is how to conditionally load a feature module on an empty path.

bodorgergely Over a year ago

Did you check what is happening with debug enabled? It might shed some light on what is happening with your setup.

Ben Racicot Over a year ago

I think you might be correct that it cannot be done without hacking at the router like nircraft mentioned.

Sinuee Hernández Over a year ago

Make the path for unauthorized different from empty. On your Guard, you can handle the authentication response before return it. So in case, this is false you can use the router navigate to the unauthorized path.

Ben Racicot · Accepted Answer · 2021-12-20 20:17:30Z

It turns out that this was basically not (safely) possible until Ivy. Now in Angular 9/10 we can lazy load feature-modules without the router very easily.

StackBlitz
V13 StackBlitz Update

@Component({
    selector: 'my-app',
    templateUrl: './app.component.html',
})
export class AppComponent implements OnInit  {
    @ViewChild('container', { read: ViewContainerRef }) container: ViewContainerRef;

    constructor( 
        private compiler: Compiler,
        private injector: Injector
    ){  }

    public ngOnInit(): void {
        if (loggedin) {
            this.loadModule(await import('./lazy/lazy.module').then(m => m.LazyModule));
        } else {
            this.loadModule(await import('./lazy2/lazy2.module').then(m => m.Lazy2Module));
        }
    }

    async loadModule(module: Type<any>) {
        let ref;
        try {
            this.container.clear();

            // Angular < 13 
            const moduleFactory = await this.compiler.compileModuleAsync(module);
            const moduleRef: any = moduleFactory.create(this.injector);
            const componentFactory = moduleRef.instance.resolveComponent(); // ASSERTION ERROR
            ref = this.container.createComponent(componentFactory, null, moduleRef.injector);

            // Angular 13 update
            const moduleRef = createNgModuleRef(module, this.injector);
            const componentFactory = moduleRef.instance.resolveComponent();
            ref = container.createComponent(
                componentFactory,
                undefined,
                moduleRef.injector
            );

        } catch (e) {
            console.error(e);
        }
            return ref;
        }
    }

For Angular 13/14 etc see the updates here stackoverflow.com/questions/70204754/…

M M · Accepted Answer · 2019-01-09 12:57:41Z

0

I believe what you intend to achieve is not possible through guards. Angular searches the routes array from top to bottom and as soon as it gets a path match, the corresponding module/component is loaded. In your case, { path: '', loadChildren: './feed/feed.module#FeedModule', canActivate: [IsAuthenticationGuard] } is a url path match and thus Angular loads the Feed Module, however does not display anything as the guard returns failure. It doesn't even proceed to check the url match for line below.

Instead what you can do is,

change the routes as { path: '', loadChildren:'./home/home.module#HomeModule', canActivate: [IsAuthenticationGuard] },
navigate to feed module if the user is authenticated succesfully. Follow this thread to get more clue on how to do this.

I hope this solves your purpose.

answered Jan 9, 2019 at 12:57

M M

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1 Comment

Ben Racicot Over a year ago

Thanks M M! Yes you can def redirect from within the guard. Especially now in 7.2 with the new UrlTree it's easier. But this would still be a common redirect. I'm talking about leveraging the same path depending on auth status.

Alex · Accepted Answer · 2019-01-05 15:37:32Z

-2

Try maybe this:

const routes: Routes = [
  { path: '', redirectTo: condition ? 'home' : 'feed', pathMatch: 'full' },
  { path: 'home', component: HomeComponent },
  { path: 'feed', component: FeedComponent },
  { path: '*', redirectTo: 'home', pathMatch: 'full' },
];

That's not directly based on Guards, but you should probably be able to get your Guard return as the condition

answered Jan 5, 2019 at 15:37

Alex

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