Angular 2 redirect if user is logged in

You want to look at the resolve property within the [Route interface].

All of the following properties are available to a route:

export interface Route {
  path?: string;
  pathMatch?: string;
  matcher?: UrlMatcher;
  component?: Type<any>;
  redirectTo?: string;
  outlet?: string;
  canActivate?: any[];
  canActivateChild?: any[];
  canDeactivate?: any[];
  canLoad?: any[];
  data?: Data;
  resolve?: ResolveData;
  children?: Routes;
  loadChildren?: LoadChildren;
  runGuardsAndResolvers?: RunGuardsAndResolvers;
  _loadedConfig?: LoadedRouterConfig;
}

resolve is designed to allow you to load some type of data before proceeding to the route. The signature for resolve looks like this:

resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot) : Observable<T>|Promise<T>|T

We can ignore that signature, however, and override it because, in this case, we want to redirect to /dashboard if the user is logged in. Otherwise, display /login route normally.

The solution is to create an injectable class and attach it to the login route's resolve property.

@Injectable()
export class IsLoggedIn {
  constructor(
    private router: Router, 
    private authService: AuthService) {
  }

  resolve(): void {
    if (this.authService.isAuthenticated) this.router.navigate(['/dashboard'])
  }
}

On your /login route, add the resolve property.

{
  path: 'login',
  component: LoginComponent,
  resolve: [IsLoggedIn]
}

Import the class in AppModule and add it to providers.

providers: [
  IsLoggedIn
]

Now anytime a logged in user attempts to go to /login, they'll be redirected to /dashboard without seeing the login page.

In this case I would probably redirect everything to DashboardComponent using

{path: '', redirectTo: 'dashboard', pathMatch: 'full'}

and than the dashboard component can determinate if the user is logged in or not (as it has AuthGuard active), and if the user is not logged in it would redirect him to login.

Probably the quickest thing to do is to tweak your LoginComponent.

Given that this.authService.isLoggedIn() returns a boolean. In your LoginComponent you can quickly check the state in ngOnInit as below:

import { Component, OnInit } from '@angular/core';
import { Router, ActivatedRoute } from '@angular/router';

import {AuthService} from '<path_to_your_auth_service>';

@Component({
  selector: 'app-login',
  templateUrl: './login.component.html',
  styleUrls: ['./login.component.scss'],
  providers: []
})
export class LoginComponent implements OnInit {
  constructor(
    private _route: ActivatedRoute,
    private _router: Router,
    private _authService: AuthService
  )

  ngOnInit() {
    // get return url from route parameters or default to '/'
    this.returnUrl = this._route.snapshot.queryParams['returnUrl'] || '/';

    // CHECK THE isLoggedIn STATE HERE 
    if (this._authService.isLoggedIn()) {
      this._router.navigate([this.returnUrl]);
    }

  }

  // Rest fo the logic here like login etc

  login() { }

}

Note that you're only adding this to ngOnInit

if (this._authService.isLoggedIn()) {
  this._router.navigate([this.returnUrl]);
}