What is in Angular 6 routing? Explain it with example.

At the moment, in our angular project, we only have one component and that is the root component - AppComponent. Now, let's create the following 2 components, so we can setup routing to navigate between these components.

• CreateEmployeeComponent
• ListEmployeesComponent

Use the following 2 Angular CLI commands to create the components.

ng g c employee/create-employee --spec=false --flat=true

ng g c employee/list-employees --spec=false --flat=true

Step 1 : Set <base href="/"> in index.html : When setting up routing in an angular application, the first step is to set the base path using the base href element. The base path tells the angular router, how to compose navigation URLs. When you create a new Angular 6 project, this is included automatically by the Angular CLI. To understand the significance of this base element, please watch Part 4 from Angular CRUD tutorial.

Step 2 : Create a separate routing module : The first question that comes to our mind is - Why should we define routes in a separate routing module.

Well, for separation of concerns and maintainability. If routing is in it's own module, it is easier to find and change routing code if required. 

Now, using the Angular CLI, let's create the routing module. By convention, the routing module class name is called AppRoutingModule and the file is named app-routing.module.ts.

ng generate module app-routing --flat=true --module=app

--module=app tells the Angular CLI to import and register routing module in the application root module AppModule.

The above command can also be written using it's short-hand notation as shown below

ng g m app-routing --flat=true -m=app

Step 3 : Import the Angular RouterModule into the AppRoutingModule and configure the application routes : Here is the modified AppRoutingModule file (app-routing.module.ts). Please note that, the CommonModule is not required in the routing module, so I have deleted it's reference. We generally don't declare components in the routing module so, I also deleted declarations array from @NgModule decorator. The rest of the code is commented and self-explanatory.

import { NgModule } from '@angular/core';

import { RouterModule, Routes } from '@angular/router';

// Import the components so they can be referenced in routes

import { CreateEmployeeComponent } from './employee/create-employee.component';

import { ListEmployeesComponent } from './employee/list-employees.component';

// The last route is the empty path route. This specifies

// the route to redirect to if the client side path is empty.

const appRoutes: Routes = [

  { path: 'list', component: ListEmployeesComponent },

  { path: 'create', component: CreateEmployeeComponent },

  { path: '', redirectTo: '/list', pathMatch: 'full' }

];

// Pass the configured routes to the forRoot() method

// to let the angular router know about our routes

// Export the imported RouterModule so router directives

// are available to the module that imports this AppRoutingModule

@NgModule({

  imports: [ RouterModule.forRoot(appRoutes) ],

  exports: [ RouterModule ]

})

export class AppRoutingModule { }

Step 4 : In the application root component file (app.component.html), create the navigation menu and tie the configured routes to it. The directive tells the router where to display routed views.

<div class="container">

    <nav class="navbar navbar-default">

        <ul class="nav navbar-nav">

            <li>

                <a routerLinkActive="active" routerLink="list">List</a>

            </li>

            <li>

                <a routerLinkActive="active" routerLink="create">Create</a>

            </li>

        </ul>

    </nav>

    <router-outlet></router-outlet>

</div>