Angular is a popular web development framework that offers many features and functionalities out of the box to help build robust and scalable applications. One of the many features of Angular is the Angular Guard. In this tutorial, we will dive into Angular Guards and how they can be used to secure and protect our Angular applications.

### What are Angular Guards?

Angular Guards are a set of interfaces that can be used to implement certain checks before allowing a user to navigate to a specific route. These checks can include tasks like checking if the user is authenticated, if they have the proper permission to access protected routes, or if the route is accessible at all.

There are four types of Angular Guards:

1. CanActivate: This guard is used to determine if a user has access to a given route.
2. CanActivateChild: This guard is used to determine if a user has access to child routes nested within a given route.
3. CanDeactivate: This guard is used to determine if a user can leave a given route.
4. CanLoad: This guard is used to determine if a user can load a given lazy-loaded feature module.

### How to implement canActivate Guard

Before we dive into implementation, let’s take a look at what we are aiming to achieve when implementing the CanActivate guard. For instance, when a user is trying to access the orders page in an e-commerce application, we want to check if the user is authenticated before allowing access.

To achieve this, start by creating a new Angular project using the command:

“`bash
ng new angular-guard-example
“`

Next, define the user authentication logic in the app component:

“`typescript
export class AppComponent {
  isUserAuthenticated = false;

  toggleUserAuthentication() {
    this.isUserAuthenticated = !this.isUserAuthenticated;
  }
}
“`

The toggleUserAuthentication method changes the value of isUserAuthenticated to determine if the user is authenticated. We will use this value in the CanActivate guard.

Next, create a new Angular guard using the command:

“`bash
ng generate guard guards/auth
“`

This command generates an auth guard in the guards directory with a default implementation that returns true. We will update this implementation to check if the user is authenticated.

“`typescript
@Injectable({
  providedIn: ‘root’
})
export class AuthGuard implements CanActivate {
  constructor(private appComponent: AppComponent, private router: Router) {}

  canActivate(
    next: ActivatedRouteSnapshot,
    state: RouterStateSnapshot): boolean {
    if (!this.appComponent.isUserAuthenticated) {
      this.router.navigate([‘/login’]);
      return false;
    }
    return true;
  }
}
“`

In the canActivate method implementation, we check if the user is authenticated and redirect them to the login page if they are not. We then return false to prevent the user from accessing the route. If they are authenticated, we simply return true to allow access.

Finally, we need to apply the guard to the route we want to secure. In app-routing.module.ts, we update the routes array to add the CanActivate guard for the orders route.

“`typescript
const routes: Routes = [
  { path: ”, redirectTo: ‘/home’, pathMatch: ‘full’ },
  { path: ‘home’, component: HomeComponent },
  { path: ‘orders’, component: OrdersComponent, canActivate: [AuthGuard] },
  { path: ‘login’, component: LoginComponent }
];
“`

Now, when a user tries to access the orders route, the canActivate method in the AuthGuard is called. If the user is authenticated, they get access to the route. If not, they are redirected to the login page.

### Common FAQs

#### 1. How do I apply multiple guards on a route?

You can apply multiple guards to a route by passing an array of guards in the canActivate, canActivateChild, canDeactivate, or canLoad properties. The guards will be executed in the order they are defined in the array, and access will only be granted if all guards pass.

#### 2. How do I skip the guard for a specific route?

You can skip the guard for a specific route by not including it in the route definition or by passing a null value in the canActivate, canActivateChild, canDeactivate, or canLoad properties.

#### 3. Can I customize the behavior of a guard based on the route parameters?

Yes, you can customize the behavior of a guard based on the route parameters by accessing the ActivatedRouteSnapshot object passed to the guard. In the canActivate method implementation, you can access the route parameters using the ActivatedRouteSnapshot object and apply custom logic based on the parameter values.

In conclusion, Angular Guards are an essential aspect of Angular development that protect our applications from unauthorized access. They provide an extra layer of security, and when used correctly, can make our applications more secure and reliable. Hopefully, this tutorial has given you a deeper understanding of Angular Guards and how to implement them.

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