angular/aio/content/tutorial/toh-pt5.md

# Add navigation with routing

The Tour of Heroes application has new requirements:

*   Add a *Dashboard* view
*   Add the ability to navigate between the *Heroes* and *Dashboard* views
*   When users click a hero name in either view, navigate to a detail view of the selected hero
*   When users click a *deep link* in an email, open the detail view for a particular hero

<div class="alert is-helpful">

For the sample application that this page describes, see the <live-example></live-example>.

</div>

When you're done, users can navigate the application like this:

<div class="lightbox">

<img alt="View navigations" src="generated/images/guide/toh/nav-diagram.png">

</div>

## Add the `AppRoutingModule`

In Angular, the best practice is to load and configure the router in a separate, top-level module.
The router is dedicated to routing and imported by the root `AppModule`.

By convention, the module class name is `AppRoutingModule` and it belongs in the `app-routing.module.ts` in the `src/app` directory.

Run `ng generate` to create the application routing module.

<code-example format="shell" language="shell">

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

</code-example>

<div class="alert is-helpful">

| Parameter      | Details |
|:---            |:---     |
| `--flat`       | Puts the file in `src/app` instead of its own directory.                   |
| `--module=app` | Tells `ng generate` to register it in the `imports` array of the `AppModule`. |

</div>

The file that `ng generate` creates looks like this:

<code-example header="src/app/app-routing.module.ts (generated)" path="toh-pt5/src/app/app-routing.module.0.ts"></code-example>

Replace it with the following:

<code-example header="src/app/app-routing.module.ts (updated)" path="toh-pt5/src/app/app-routing.module.1.ts"></code-example>

First, the `app-routing.module.ts` file imports `RouterModule` and `Routes` so the application can have routing capability.
The next import, `HeroesComponent`, gives the Router somewhere to go once you configure the routes.

Notice that the `CommonModule` references and `declarations` array are unnecessary, so are no longer part of `AppRoutingModule`.
The following sections explain the rest of the `AppRoutingModule` in more detail.

### Routes

The next part of the file is where you configure your routes.
*Routes* tell the Router which view to display when a user clicks a link or pastes a URL into the browser address bar.

Since `app-routing.module.ts` already imports `HeroesComponent`, you can use it in the `routes` array:

<code-example header="src/app/app-routing.module.ts" path="toh-pt5/src/app/app-routing.module.ts" region="heroes-route"></code-example>

A typical Angular `Route` has two properties:

| Properties  | Details |
|:---         |:---     |
| `path`      | A string that matches the URL in the browser address bar.                  |
| `component` | The component that the router should create when navigating to this route. |

This tells the router to match that URL to `path: 'heroes'` and display the `HeroesComponent` when the URL is something like `localhost:4200/heroes`.

### `RouterModule.forRoot()`

The `@NgModule` metadata initializes the router and starts it listening for browser location changes.

The following line adds the `RouterModule` to the `AppRoutingModule` `imports` array and configures it with the `routes` in one step by calling `RouterModule.forRoot()`:

<code-example header="src/app/app-routing.module.ts" path="toh-pt5/src/app/app-routing.module.ts" region="ngmodule-imports"></code-example>

<div class="alert is-helpful">

The method is called `forRoot()` because you configure the router at the application's root level.
The `forRoot()` method supplies the service providers and directives needed for routing, and performs the initial navigation based on the current browser URL.

</div>

Next, `AppRoutingModule` exports `RouterModule` to be available throughout the application.

<code-example header="src/app/app-routing.module.ts (exports array)" path="toh-pt5/src/app/app-routing.module.ts" region="export-routermodule"></code-example>

## Add `RouterOutlet`

<!-- markdownlint-disable MD001 -->

Open the `AppComponent` template and replace the `<app-heroes>` element with a `<router-outlet>` element.

<code-example header="src/app/app.component.html (router-outlet)" path="toh-pt5/src/app/app.component.html" region="outlet"></code-example>

The `AppComponent` template no longer needs `<app-heroes>` because the application only displays the `HeroesComponent` when the user navigates to it.

The `<router-outlet>` tells the router where to display routed views.

<div class="alert is-helpful">

The `RouterOutlet` is one of the router directives that became available to the `AppComponent` because `AppModule` imports `AppRoutingModule` which exported `RouterModule`.
The `ng generate` command you ran at the start of this tutorial added this import because of the `--module=app` flag.
If you didn't use the `ng generate` command to create `app-routing.module.ts`, import `AppRoutingModule` into `app.module.ts` and add it to the `imports` array of the `NgModule`.

</div>

<!-- markdownlint-disable MD024 -->

#### Try it

If you're not still serving your application, run `ng serve` to see your application in the browser.

The browser should refresh and display the application title but not the list of heroes.

Look at the browser's address bar.
The URL ends in `/`.
The route path to `HeroesComponent` is `/heroes`.

Append `/heroes` to the URL in the browser address bar.
You should see the familiar heroes overview/detail view.

Remove `/heroes` from the URL in the browser address bar.
The browser should refresh and display the application title but not the list of heroes.

<!-- markdownlint-enable MD001 -->
<!-- markdownlint-enable MD024 -->

<a id="routerlink"></a>

## Add a navigation link using `routerLink`

Ideally, users should be able to click a link to navigate rather than pasting a route URL into the address bar.

Add a `<nav>` element and, within that, an anchor element that, when clicked, triggers navigation to the `HeroesComponent`.
The revised `AppComponent` template looks like this:

<code-example header="src/app/app.component.html (heroes RouterLink)" path="toh-pt5/src/app/app.component.html" region="heroes"></code-example>

A [`routerLink` attribute](#routerlink) is set to `"/heroes"`, the string that the router matches to the route to `HeroesComponent`.
The `routerLink` is the selector for the [`RouterLink` directive](api/router/RouterLink) that turns user clicks into router navigations.
It's another of the public directives in the `RouterModule`.

The browser refreshes and displays the application title and heroes link, but not the heroes list.

Click the link.
The address bar updates to `/heroes` and the list of heroes appears.

<div class="alert is-helpful">

Make this and future navigation links look better by adding private CSS styles to `app.component.css` as listed in the [final code review](#appcomponent) below.

</div>

## Add a dashboard view

Routing makes more sense when your application has more than one view, yet
the *Tour of Heroes* application has only the heroes view.

To add a `DashboardComponent`, run `ng generate` as shown here:

<code-example format="shell" language="shell">

ng generate component dashboard

</code-example>

`ng generate` creates the files for the `DashboardComponent` and declares it in `AppModule`.

Replace the default content in these files as shown here:

<code-tabs>
    <code-pane header="src/app/dashboard/dashboard.component.html" path="toh-pt5/src/app/dashboard/dashboard.component.1.html"></code-pane>
    <code-pane header="src/app/dashboard/dashboard.component.ts" path="toh-pt5/src/app/dashboard/dashboard.component.ts"></code-pane>
    <code-pane header="src/app/dashboard/dashboard.component.css" path="toh-pt5/src/app/dashboard/dashboard.component.css"></code-pane>
</code-tabs>

The  *template* presents a grid of hero name links.

*   The `*ngFor` repeater creates as many links as are in the component's `heroes` array.
*   The links are styled as colored blocks by the `dashboard.component.css`.
*   The links don't go anywhere yet.

The *class* is like the `HeroesComponent` class.

*   It defines a `heroes` array property
*   The constructor expects Angular to inject the `HeroService` into a private `heroService` property
*   The `ngOnInit()` lifecycle hook calls `getHeroes()`

This `getHeroes()` returns the sliced list of heroes at positions 1 and 5, returning only Heroes two, three, four, and five.

<code-example header="src/app/dashboard/dashboard.component.ts" path="toh-pt5/src/app/dashboard/dashboard.component.ts" region="getHeroes"></code-example>

### Add the dashboard route

To navigate to the dashboard, the router needs an appropriate route.

Import the `DashboardComponent` in the `app-routing-module.ts` file.

<code-example header="src/app/app-routing.module.ts (import DashboardComponent)" path="toh-pt5/src/app/app-routing.module.ts" region="import-dashboard"></code-example>

Add a route to the `routes` array that matches a path to the `DashboardComponent`.

<code-example header="src/app/app-routing.module.ts" path="toh-pt5/src/app/app-routing.module.ts" region="dashboard-route"></code-example>

### Add a default route

When the application starts, the browser's address bar points to the web site's root.
That doesn't match any existing route so the router doesn't navigate anywhere.
The space below the `<router-outlet>` is blank.

To make the application navigate to the dashboard automatically, add the following route to the `routes` array.

<code-example header="src/app/app-routing.module.ts" path="toh-pt5/src/app/app-routing.module.ts" region="redirect-route"></code-example>

This route redirects a URL that fully matches the empty path to the route whose path is `'/dashboard'`.

After the browser refreshes, the router loads the `DashboardComponent` and the browser address bar shows the `/dashboard` URL.

### Add dashboard link to the shell

The user should be able to navigate between the `DashboardComponent` and the `HeroesComponent` by clicking links in the navigation area near the top of the page.

Add a dashboard navigation link to the `AppComponent` shell template, just above the *Heroes* link.

<code-example header="src/app/app.component.html" path="toh-pt5/src/app/app.component.html"></code-example>

After the browser refreshes you can navigate freely between the two views by clicking the links.

<a id="hero-details"></a>

## Navigating to hero details

The `HeroDetailComponent` displays details of a selected hero.
At the moment the `HeroDetailComponent` is only visible at the bottom of the `HeroesComponent`

The user should be able to get to these details in three ways.

1.  By clicking a hero in the dashboard.
1.  By clicking a hero in the heroes list.
1.  By pasting a "deep link" URL into the browser address bar that identifies the hero to display.

This section enables navigation to the `HeroDetailComponent` and liberate it from the `HeroesComponent`.

### Delete *hero details* from `HeroesComponent`

When the user clicks a hero in `HeroesComponent`, the application should navigate to the `HeroDetailComponent`, replacing the heroes list view with the hero detail view.
The heroes list view should no longer show hero details as it does now.

Open the `heroes/heroes.component.html` and delete the `<app-hero-detail>` element from the bottom.

Clicking a hero item now does nothing.
You can fix that after you enable routing to the `HeroDetailComponent`.

### Add a *hero detail* route

A URL like `~/detail/11` would be a good URL for navigating to the *Hero Detail* view of the hero whose `id` is `11`.

Open `app-routing.module.ts` and import `HeroDetailComponent`.

<code-example header="src/app/app-routing.module.ts (import HeroDetailComponent)" path="toh-pt5/src/app/app-routing.module.ts" region="import-herodetail"></code-example>

Then add a *parameterized* route to the `routes` array that matches the path pattern to the *hero detail* view.

<code-example header="src/app/app-routing.module.ts" path="toh-pt5/src/app/app-routing.module.ts" region="detail-route"></code-example>

The colon `:` character in the `path` indicates that `:id` is a placeholder for a specific hero `id`.

At this point, all application routes are in place.

<code-example header="src/app/app-routing.module.ts (all routes)" path="toh-pt5/src/app/app-routing.module.ts" region="routes"></code-example>

### `DashboardComponent` hero links

The `DashboardComponent` hero links do nothing at the moment.

Now that the router has a route to `HeroDetailComponent`, fix the dashboard hero links to navigate using the *parameterized* dashboard route.

<code-example header="src/app/dashboard/dashboard.component.html (hero links)" path="toh-pt5/src/app/dashboard/dashboard.component.html" region="click"></code-example>

You're using Angular [interpolation binding](guide/interpolation) within the `*ngFor` repeater to insert the current iteration's `hero.id` into each [`routerLink`](#routerlink).

<a id="heroes-component-links"></a>

### `HeroesComponent` hero links

The hero items in the `HeroesComponent` are `<li>` elements whose click events are bound to the component's `onSelect()` method.

<code-example header="src/app/heroes/heroes.component.html (list with onSelect)" path="toh-pt4/src/app/heroes/heroes.component.html" region="list"></code-example>

Remove the `<li>` back to just its `*ngFor`.
Wrap the badge and name in an anchor `<a>` element.
Add a `routerLink` attribute to the anchor that's the same as in the dashboard template.

<code-example header="src/app/heroes/heroes.component.html (list with links)" path="toh-pt5/src/app/heroes/heroes.component.html" region="list"></code-example>

Be sure to fix the private style sheet in `heroes.component.css` to make the list look as it did before.
Revised styles are in the [final code review](#heroescomponent) at the bottom of this guide.

#### Remove dead code - optional

While the `HeroesComponent` class still works, the `onSelect()` method and `selectedHero` property are no longer used.

It's nice to tidy things up for your future self.
Here's the class after pruning away the dead code.

<code-example header="src/app/heroes/heroes.component.ts (cleaned up)" path="toh-pt5/src/app/heroes/heroes.component.ts" region="class"></code-example>

## Routable `HeroDetailComponent`

The parent `HeroesComponent` used to set the `HeroDetailComponent.hero` property and the `HeroDetailComponent` displayed the hero.

`HeroesComponent` doesn't do that anymore.
Now the router creates the `HeroDetailComponent` in response to a URL such as `~/detail/12`.

The `HeroDetailComponent` needs a new way to get the hero to display.
This section explains the following:

*   Get the route that created it
*   Extract the `id` from the route
*   Get the hero with that `id` from the server using the `HeroService`

Add the following imports:

<code-example header="src/app/hero-detail/hero-detail.component.ts" path="toh-pt5/src/app/hero-detail/hero-detail.component.ts" region="added-imports"></code-example>

<a id="hero-detail-ctor"></a>

Inject the `ActivatedRoute`, `HeroService`, and `Location` services into the constructor, saving their values in private fields:

<code-example header="src/app/hero-detail/hero-detail.component.ts" path="toh-pt5/src/app/hero-detail/hero-detail.component.ts" region="ctor"></code-example>

The [`ActivatedRoute`](api/router/ActivatedRoute) holds information about the route to this instance of the `HeroDetailComponent`.
This component is interested in the route's parameters extracted from the URL.
The "id" parameter is the `id` of the hero to display.

The [`HeroService`](tutorial/toh-pt4) gets hero data from the remote server and this component uses it to get the hero-to-display.

The [`location`](api/common/Location) is an Angular service for interacting with the browser.
This service lets you navigate back to the previous view.

### Extract the `id` route parameter

In the `ngOnInit()` [lifecycle hook](guide/lifecycle-hooks#oninit) call `getHero()` and define it as follows.

<code-example header="src/app/hero-detail/hero-detail.component.ts" path="toh-pt5/src/app/hero-detail/hero-detail.component.ts" region="ngOnInit"></code-example>

The `route.snapshot` is a static image of the route information shortly after the component was created.

The `paramMap` is a dictionary of route parameter values extracted from the URL.
The `"id"` key returns the `id` of the hero to fetch.

Route parameters are always strings.
The JavaScript `Number` function converts the string to a number,
which is what a hero `id` should be.

The browser refreshes and the application crashes with a compiler error.
`HeroService` doesn't have a `getHero()` method.
Add it now.

### Add `HeroService.getHero()`

Open `HeroService` and add the following `getHero()` method with the `id` after the `getHeroes()` method:

<code-example header="src/app/hero.service.ts (getHero)" path="toh-pt5/src/app/hero.service.ts" region="getHero"></code-example>

<div class="alert is-important">

**IMPORTANT**: <br />
The backtick \( <code>&grave;</code> \) characters define a JavaScript [template literal](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Template_literals) for embedding the `id`.

</div>

Like [`getHeroes()`](tutorial/toh-pt4#observable-heroservice), `getHero()` has an asynchronous signature.
It returns a *mock hero* as an `Observable`, using the RxJS `of()` function.

You can rewrite `getHero()` as a real `Http` request without having to change the `HeroDetailComponent` that calls it.

<!-- markdownlint-disable MD024 -->

#### Try it

The browser refreshes and the application is working again.
You can click a hero in the dashboard or in the heroes list and navigate to that hero's detail view.

If you paste `localhost:4200/detail/12` in the browser address bar, the router navigates to the detail view for the hero with `id: 12`, **Dr Nice**.

<!-- markdownlint-enable MD024 -->

<a id="goback"></a>

### Find the way back

By clicking the browser's back button, you can go back to the previous page. This could be the hero list or dashboard view, depending upon which sent you to the detail view.

It would be nice to have a button on the `HeroDetail` view that can do that.

Add a *go back* button to the bottom of the component template and bind it to the component's `goBack()` method.

<code-example header="src/app/hero-detail/hero-detail.component.html (back button)" path="toh-pt5/src/app/hero-detail/hero-detail.component.html" region="back-button"></code-example>

Add a `goBack()` *method* to the component class that navigates backward one step in the browser's history stack
using the `Location` service that you [used to inject](#hero-detail-ctor).

<code-example header="src/app/hero-detail/hero-detail.component.ts (goBack)" path="toh-pt5/src/app/hero-detail/hero-detail.component.ts" region="goBack"></code-example>

Refresh the browser and start clicking.
Users can now navigate around the application using the new buttons.

The details look better when you add the private CSS styles to `hero-detail.component.css` as listed in one of the ["final code review"](#final-code-review) tabs below.

## Final code review

<!-- markdownlint-disable MD001 -->

Here are the code files discussed on this page.

<a id="approutingmodule"></a>
<a id="appmodule"></a>

#### `AppRoutingModule`, `AppModule`, and `HeroService`

<code-tabs>
    <code-pane header="src/app/app.module.ts" path="toh-pt5/src/app/app.module.ts"></code-pane>
    <code-pane header="src/app/app-routing.module.ts" path="toh-pt5/src/app/app-routing.module.ts"></code-pane>
    <code-pane header="src/app/hero.service.ts" path="toh-pt5/src/app/hero.service.ts"></code-pane>
</code-tabs>

<a id="appcomponent"></a>

#### `AppComponent`

<code-tabs>
    <code-pane header="src/app/app.component.html" path="toh-pt5/src/app/app.component.html"></code-pane>
    <code-pane header="src/app/app.component.ts" path="toh-pt5/src/app/app.component.ts"></code-pane>
    <code-pane header="src/app/app.component.css" path="toh-pt5/src/app/app.component.css"></code-pane>
</code-tabs>

<a id="dashboardcomponent"></a>

#### `DashboardComponent`

<code-tabs>
    <code-pane header="src/app/dashboard/dashboard.component.html" path="toh-pt5/src/app/dashboard/dashboard.component.html"></code-pane>
    <code-pane header="src/app/dashboard/dashboard.component.ts" path="toh-pt5/src/app/dashboard/dashboard.component.ts"></code-pane>
    <code-pane header="src/app/dashboard/dashboard.component.css" path="toh-pt5/src/app/dashboard/dashboard.component.css"></code-pane>
</code-tabs>

<a id="heroescomponent"></a>

#### `HeroesComponent`

<code-tabs>
    <code-pane header="src/app/heroes/heroes.component.html" path="toh-pt5/src/app/heroes/heroes.component.html"></code-pane>
    <code-pane header="src/app/heroes/heroes.component.ts" path="toh-pt5/src/app/heroes/heroes.component.ts"></code-pane>
    <code-pane header="src/app/heroes/heroes.component.css" path="toh-pt5/src/app/heroes/heroes.component.css"></code-pane>
</code-tabs>

<a id="herodetailcomponent"></a>

#### `HeroDetailComponent`

<code-tabs>
    <code-pane header="src/app/hero-detail/hero-detail.component.html" path="toh-pt5/src/app/hero-detail/hero-detail.component.html"></code-pane>
    <code-pane header="src/app/hero-detail/hero-detail.component.ts" path="toh-pt5/src/app/hero-detail/hero-detail.component.ts"></code-pane>
    <code-pane header="src/app/hero-detail/hero-detail.component.css" path="toh-pt5/src/app/hero-detail/hero-detail.component.css"></code-pane>
</code-tabs>

<!-- markdownlint-enable MD001 -->

## Summary

*   You added the Angular router to navigate among different components
*   You turned the `AppComponent` into a navigation shell with `<a>` links and a `<router-outlet>`
*   You configured the router in an `AppRoutingModule`
*   You defined routes, a redirect route, and a parameterized route
*   You used the `routerLink` directive in anchor elements
*   You refactored a tightly coupled main/detail view into a routed detail view
*   You used router link parameters to navigate to the detail view of a user-selected hero
*   You shared the `HeroService` with other components

@reviewed 2022-02-28