UI-Router for AngularJS (1.x) - Hello Solar System!

In this tutorial, we will build on Hello World! and create a slightly more ambitious Hello Solar System app.

We will implement a list/detail interface, also known as master-detail. To accomplish this, we will create two new application states:

  • The people state will show a list of all the people.
  • The person state will show details for a specific person.

Additionally, we will switch our views from templates to AngularJS 1.5 components.

At any time, the user can click “reload plunker”, and the app will restart at the same URL. The URL contains the information necessary to restore the application’s state. When the app is restarted, it will be in the same state as before.

Plunker embeds can time out. If you get a “Not Found” response, your plunker embed has timed out. Click the “Refresh” icon to get a new plunker, then try experimenting with the “reload plunker” button again.

Live demo

Take a look at the completed Hello Solar System live demo below. Click the ui-sref labeled “People” to view the list of all people. Click a person to view the person details.

As you navigate through the app, the UI-Router State Visualizer shows the current state


New concepts

This app introduces some new concepts and UI-Router features.

Route to component

Although UI-Router allows you to define your views using arbitrary template and controller combinations, we recommend instead that you adopt a component based architecture.

AngularJS 1.5 introduced the .component(), which is a special class of directives. A component encapsulates a template and a controller as a single unit, and also explicitly defines its inputs (data) and outputs (events). To learn more, read the official AngularJS 1.5+ component docs, and explore a blog or two.


To route to a component that you have created, add a component: 'myComponentName' property on your state definition (and do not use template: or controller: properties).

The Hello Solar System hello component:

angular.module('hellogalaxy').component('hello', {
  template:  '<h3>{{$ctrl.greeting}} Solar System!</h3>' +
             '<button ng-click="$ctrl.toggleGreeting()">toggle greeting</button>',
           
  controller: function() {
    this.greeting = 'hello';
  
    this.toggleGreeting = function() {
      this.greeting = (this.greeting == 'hello') ? 'whats up' : 'hello'
    }
  }
})

… and the Hello Solar System hello state definition:

var helloGalaxy = {
  name: 'hello',
  url: '/hello',
  component: 'hello'
}

The string 'hello' in component: 'hello' is used to reference the component that you registered with angular, i.e., .component('hello', ...)

Resolve data

When a user switches back and forth between states of a single page web app, the app often needs to fetch application data from a server API, such as a REST endpoint.

A state can specify the data it requires by using a resolve: block. When the user tries to activate a state which has a resolve: block, UI-Router will fetch the required data before activating the state.

An AngularJS (1.x) resolve: block is an object on a state definition. Each key is the name of some data to load, and each value is a function which returns a promise for the data.
Resolve functions are injected using Angular’s injector.

The Hello Solar System people state has a resolve block:

var peopleState = {
  name: 'people',
  url: '/people',
  component: 'people',
  resolve: {
    people: function(PeopleService) {
      return PeopleService.getAllPeople();
    }
  }
},

When fetching data, we recommend delegating to services which return promises.

After the data has been fetched, it is mapped to the component’s input bindings: by name. The Hello Solar System people component has a bindings: with an input people that matches the resolve’s name:

angular.module('hellogalaxy').component('people', {
  bindings: { people: '<' },

  template: '<h3>Some people:</h3>' +
            '<ul>' +
            '  <li ng-repeat="person in $ctrl.people">' +
            '    <a ui-sref="person({ personId: person.id })">' +
            '      {{person.name}}' +
            '    </a>' +
            '  </li>' +
            '</ul>'
})

UI-Router waits until the promise returned from PeopleService.getAllPeople() resolves before activating the people state. Then, it feeds the list of people into the people component’s people: binding. It inserts the people component into the <ui-view> viewport.

State Parameters

We also want to allow the user to be able view the details for a specific person. The person state takes a personId parameter, and uses it to fetch that specific person’s details.

The parameter value is included as a part of the URL. This enables the same person details to be shown when the plunker is reloaded.

The person state definition:

{
  name: 'person',
  url: '/people/{personId}',
  component: 'person',
  resolve: {
    person: function(PeopleService, $transition$) {
      return PeopleService.getPerson($transition$.params().personId);
    }
  }
}

The URL will reflect the current personId parameter value, e.g., /people/21

The resolve delegates to PeopleService to fetch the correct person. It passes the personId parameter, which it received from the $transition$ object. The $transition$ is a special injectable object with information about the current state transition.

Linking with params

Note that our app’s main Navigation Bar links to three states: hello, about, and people, but it doesn’t include a link directly to the person state. This is because the state cannot be activated without a parameter value for the personId parameter.

In the people state we create links to the person state. We create a link for each person in the people list. We still create the link using ui-sref, but we include the personId parameter value. As we ng-repeat over each person object, we use the object’s .id property in the ui-sref.

  <li ng-repeat="person in $ctrl.people">
    <a ui-sref="person({ personId: person.id })">
      {{person.name}}
    </a>
  </li>

To pass parameters to a state using ui-sref, add parenthesis after the state name.
An expression string inside the parenthesis is used as the target state parameter key/value pairs. The expression is evaluated against the enclosing scope.