Display a selection list

This tutorial shows you how to:

• Expand the Tour of Heroes application to display a list of heroes.
• Allow users to select a hero and display the hero's details.

For the sample application that this page describes, see the live example.

Create mock heroes

The first step is to create some heroes to display.

Create a file called mock-heroes.ts in the src/app/ directory. Define a HEROES constant as an array of ten heroes and export it. The file should look like this.

import { Hero } from './hero';

export const HEROES: Hero[] = [
  { id: 12, name: 'Dr. Nice' },
  { id: 13, name: 'Bombasto' },
  { id: 14, name: 'Celeritas' },
  { id: 15, name: 'Magneta' },
  { id: 16, name: 'RubberMan' },
  { id: 17, name: 'Dynama' },
  { id: 18, name: 'Dr. IQ' },
  { id: 19, name: 'Magma' },
  { id: 20, name: 'Tornado' }
];

Displaying heroes

Open the HeroesComponent class file and import the mock HEROES.

import { HEROES } from '../mock-heroes';

In HeroesComponent class, define a component property called heroes to expose the HEROES array for binding.

export class HeroesComponent implements OnInit {

  heroes = HEROES;
}

List heroes with *ngFor

Open the HeroesComponent template file and make the following changes:

1. Add an <h2> at the top.
2. Below the <h2>, add a <ul> element.
3. In the <ul> element, insert an <li>.
4. Place a <button> inside the <li> that displays properties of a hero inside <span> elements.
5. Add CSS classes to style the component.

to look like this:

<h2>My Heroes</h2>
<ul class="heroes">
  <li>
    <button type="button">
      <span class="badge">{{hero.id}}</span>
      <span class="name">{{hero.name}}</span>
    </button>
  </li>
</ul>

That displays an error since the hero property doesn't exist. To have access to each individual hero and list them all, add an *ngFor to the <li> to iterate through the list of heroes:

<li *ngFor="let hero of heroes">

The *ngFor is Angular's repeater directive. It repeats the host element for each element in a list.

The syntax in this example is as follows:

Don't forget to put the asterisk * in front of ngFor. It's a critical part of the syntax.

After the browser refreshes, the list of heroes appears.

Style the heroes

The heroes list should be attractive and should respond visually when users hover over and select a hero from the list.

In the first tutorial, you set the basic styles for the entire application in styles.css. That style sheet didn't include styles for this list of heroes.

You could add more styles to styles.css and keep growing that style sheet as you add components.

You may prefer instead to define private styles for a specific component. This keeps everything a component needs, such as the code, the HTML, and the CSS, together in one place.

This approach makes it easier to re-use the component somewhere else and deliver the component's intended appearance even if the global styles are different.

You define private styles either inline in the @Component.styles array or as style sheet files identified in the @Component.styleUrls array.

When the ng generate created the HeroesComponent, it created an empty heroes.component.css style sheet for the HeroesComponent and pointed to it in @Component.styleUrls like this.

@Component({
  selector: 'app-heroes',
  templateUrl: './heroes.component.html',
  styleUrls: ['./heroes.component.css']
})

Open the heroes.component.css file and paste in the private CSS styles for the HeroesComponent from the final code review.

Styles and style sheets identified in @Component metadata are scoped to that specific component. The heroes.component.css styles apply only to the HeroesComponent and don't affect the outer HTML or the HTML in any other component.

Viewing details

When the user clicks a hero in the list, the component should display the selected hero's details at the bottom of the page.

The code in this section listens for the hero item click event and display/update the hero details.

Add a click event binding

Add a click event binding to the <button> in the <li> like this:

<li *ngFor="let hero of heroes">
  <button type="button" (click)="onSelect(hero)">
  <!-- ... -->

This is an example of Angular's event binding syntax.

The parentheses around click tell Angular to listen for the <button> element's click event. When the user clicks in the <button>, Angular executes the onSelect(hero) expression.

In the next section, define an onSelect() method in HeroesComponent to display the hero that was defined in the *ngFor expression.

Add the click event handler

Rename the component's hero property to selectedHero but don't assign any value to it since there is no selected hero when the application starts.

Add the following onSelect() method, which assigns the clicked hero from the template to the component's selectedHero.

selectedHero?: Hero;
onSelect(hero: Hero): void {
  this.selectedHero = hero;
}

Add a details section

Currently, you have a list in the component template. To show details about a hero when you click their name in the list, add a section in the template that displays their details. Add the following to heroes.component.html beneath the list section:

<div *ngIf="selectedHero">
  <h2>{{selectedHero.name | uppercase}} Details</h2>
  <div>id: {{selectedHero.id}}</div>
  <div>
    <label for="hero-name">Hero name: </label>
    <input id="hero-name" [(ngModel)]="selectedHero.name" placeholder="name">
  </div>
</div>

The hero details should only be displayed when a hero is selected. When a component is created initially, there is no selected hero. Add the *ngIf directive to the <div> that wraps the hero details. This directive tells Angular to render the section only when the selectedHero is defined after it has been selected by clicking on a hero.

Don't forget the asterisk * character in front of ngIf. It's a critical part of the syntax.

Style the selected hero

To help identify the selected hero, you can use the .selected CSS class in the styles you added earlier. To apply the .selected class to the <li> when the user clicks it, use class binding.

Angular's class binding can add and remove a CSS class conditionally. Add [class.some-css-class]="some-condition" to the element you want to style.

Add the following [class.selected] binding to the <button> in the HeroesComponent template:

[class.selected]="hero === selectedHero"

When the current row hero is the same as the selectedHero, Angular adds the selected CSS class. When the two heroes are different, Angular removes the class.

The finished <li> looks like this:

<li *ngFor="let hero of heroes">
  <button [class.selected]="hero === selectedHero" type="button" (click)="onSelect(hero)">
    <span class="badge">{{hero.id}}</span>
    <span class="name">{{hero.name}}</span>
  </button>
</li>

Final code review

Here are the code files discussed on this page, including the HeroesComponent styles.

import { Hero } from './hero';

export const HEROES: Hero[] = [
  { id: 12, name: 'Dr. Nice' },
  { id: 13, name: 'Bombasto' },
  { id: 14, name: 'Celeritas' },
  { id: 15, name: 'Magneta' },
  { id: 16, name: 'RubberMan' },
  { id: 17, name: 'Dynama' },
  { id: 18, name: 'Dr. IQ' },
  { id: 19, name: 'Magma' },
  { id: 20, name: 'Tornado' }
];

import { Component, OnInit } from '@angular/core';
import { Hero } from '../hero';
import { HEROES } from '../mock-heroes';

@Component({
  selector: 'app-heroes',
  templateUrl: './heroes.component.html',
  styleUrls: ['./heroes.component.css']
})

export class HeroesComponent implements OnInit {

  heroes = HEROES;
  selectedHero?: Hero;

  constructor() { }

  ngOnInit(): void {
  }

  onSelect(hero: Hero): void {
    this.selectedHero = hero;
  }
}

<h2>My Heroes</h2>
<ul class="heroes">
  <li *ngFor="let hero of heroes">
    <button [class.selected]="hero === selectedHero" type="button" (click)="onSelect(hero)">
      <span class="badge">{{hero.id}}</span>
      <span class="name">{{hero.name}}</span>
    </button>
  </li>
</ul>

<div *ngIf="selectedHero">
  <h2>{{selectedHero.name | uppercase}} Details</h2>
  <div>id: {{selectedHero.id}}</div>
  <div>
    <label for="hero-name">Hero name: </label>
    <input id="hero-name" [(ngModel)]="selectedHero.name" placeholder="name">
  </div>
</div>

/* HeroesComponent's private CSS styles */
.heroes {
  margin: 0 0 2em 0;
  list-style-type: none;
  padding: 0;
  width: 15em;
}

.heroes li {
  display: flex;
}

.heroes button {
  flex: 1;
  cursor: pointer;
  position: relative;
  left: 0;
  background-color: #EEE;
  margin: .5em;
  padding: 0;
  border-radius: 4px;
  display: flex;
  align-items: stretch;
  height: 1.8em;
}

.heroes button:hover {
  color: #2c3a41;
  background-color: #e6e6e6;
  left: .1em;
}

.heroes button:active {
  background-color: #525252;
  color: #fafafa;
}

.heroes button.selected {
  background-color: black;
  color: white;
}

.heroes button.selected:hover {
  background-color: #505050;
  color: white;
}

.heroes button.selected:active {
  background-color: black;
  color: white;
}

.heroes .badge {
  display: inline-block;
  font-size: small;
  color: white;
  padding: 0.8em 0.7em 0 0.7em;
  background-color: #405061;
  line-height: 1em;
  margin-right: .8em;
  border-radius: 4px 0 0 4px;
}

.heroes .name {
  align-self: center;
}

Summary

• The Tour of Heroes application displays a list of heroes with a detail view.
• The user can select a hero and see that hero's details.
• You used *ngFor to display a list.
• You used *ngIf to conditionally include or exclude a block of HTML.
• You can toggle a CSS style class with a class binding.