What is Angular routing and how do you implement it in Angular 8?

Basic

What is Angular routing and how do you implement it in Angular 8?

Overview

Angular routing allows for navigation from one view to the next as users perform application tasks. It's a crucial feature in single-page applications (SPAs) where the page does not reload during navigation. Angular 8 introduces some new features and improvements in routing, making it more efficient and easier to manage.

Key Concepts

  1. RouterModule: A built-in module that Angular uses for routing.
  2. Routes: Defines an array of route definitions.
  3. RouterOutlet: A directive used to specify where routed views will be displayed.

Common Interview Questions

Basic Level

  1. What is Angular Routing?
  2. How do you configure basic routing in an Angular 8 application?

Intermediate Level

  1. How do you pass and retrieve parameters using Angular 8 routing?

Advanced Level

  1. What are route guards in Angular 8, and how do you implement them?

Detailed Answers

1. What is Angular Routing?

Answer: Angular Routing is a feature that allows Angular applications to enable navigation from one view to another while maintaining the application state. It changes the browser's URL as the user navigates through the app, without reloading the page. This is a core part of single-page applications (SPAs) where the entire application is loaded in a single HTML page, and navigation is handled through JavaScript and the Angular framework.

Key Points:
- Enables navigation between views/components.
- Manipulates browser history and URL.
- Supports lazy loading, improving application performance.

Example:

// Angular does not use C#, so a direct code example in C# for Angular routing cannot be provided. Angular uses TypeScript for its configuration and components.

2. How do you configure basic routing in an Angular 8 application?

Answer: Configuring basic routing in Angular 8 involves defining routes in the AppRoutingModule, importing RouterModule and Routes from @angular/router, and then specifying routes in a Routes array. Each route maps a URL path to a component.

Key Points:
- Define routes in AppRoutingModule.
- Use RouterModule.forRoot(routes) to import your routes into the application.
- Utilize <router-outlet></router-outlet> in the component template to display the routed views.

Example:

// app-routing.module.ts
import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';
import { HomeComponent } from './home/home.component';
import { AboutComponent } from './about/about.component';

const routes: Routes = [
  { path: 'home', component: HomeComponent },
  { path: 'about', component: AboutComponent },
  { path: '', redirectTo: '/home', pathMatch: 'full' },
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule { }

<!-- In your AppComponent template -->
<router-outlet></router-outlet>

3. How do you pass and retrieve parameters using Angular 8 routing?

Answer: Parameters can be passed through routes using route parameters or query parameters. To retrieve these parameters in the destination component, Angular provides the ActivatedRoute service.

Key Points:
- Route parameters are part of the URL path, while query parameters are appended to the URL with a '?'.
- Use ActivatedRoute to access parameters in the routed component.

Example:

// Defining a route with a parameter
const routes: Routes = [
  { path: 'profile/:id', component: ProfileComponent },
];

// In ProfileComponent, retrieving the parameter
import { ActivatedRoute } from '@angular/router';

constructor(private route: ActivatedRoute) { 
  this.route.params.subscribe(params => {
    console.log(params['id']); // Log the value of id
  });
}

4. What are route guards in Angular 8, and how do you implement them?

Answer: Route guards in Angular are interfaces that can be implemented to control navigation into or away from a route. They are useful for permissions and other pre-navigation logic, such as authentication checks.

Key Points:
- Commonly used route guards include CanActivate, CanDeactivate, and Resolve.
- Guards are provided to the routing configuration using the canActivate and canDeactivate properties among others.

Example:

import { Injectable } from '@angular/core';
import { CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot, UrlTree } from '@angular/router';
import { Observable } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class AuthGuard implements CanActivate {
  canActivate(
    next: ActivatedRouteSnapshot,
    state: RouterStateSnapshot): Observable<boolean | UrlTree> | Promise<boolean | UrlTree> | boolean | UrlTree {
    // Your authentication logic here
    return true; // or false based on the logic
  }
}

// In your routing module
const routes: Routes = [
  { path: 'secured', component: SecuredComponent, canActivate: [AuthGuard] },
];

Note: The provided code samples are in TypeScript, which is used in Angular applications, not C#. Angular applications are primarily written in TypeScript for better integration with Angular's features and tooling.

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