Services

Services

An Ember.Service is an Ember object that lives for the duration of the application, and can be made available in different parts of your application.

Services are useful for features that require shared state or persistent connections. Example uses of services might include:

• User/session authentication.
• Geolocation.
• WebSockets.
• Server-sent events or notifications.
• Server-backed API calls that may not fit Ember Data.
• Third-party APIs.
• Logging.

Defining Services

Services can be generated using Ember CLI's service generator. For example, the following command will create the ShoppingCart service:

ember generate service shopping-cart

Services must extend the Ember.Service base class:

import Ember from 'ember';

export default Ember.Service.extend({
});

Like any Ember object, a service is initialized and can have properties and methods of its own. Below, the shopping cart service manages an items array that represents the items currently in the shopping cart.

import Ember from 'ember';

export default Ember.Service.extend({
  items: null,

  init() {
    this._super(...arguments);
    this.set('items', []);
  },

  add(item) {
    this.get('items').pushObject(item);
  },

  remove(item) {
    this.get('items').removeObject(item);
  },

  empty() {
    this.get('items').clear();
  }
});

Accessing Services

To access a service, you can inject it in any container-resolved object such as a component or another service using the Ember.inject.service function. There are 2 ways to use this function. You can either invoke it with no arguments, or you can pass it the registered name of the service. When no arguments are passed, the service is loaded based on the name of the variable key. You can load the shopping cart service with no arguments like below.

import Ember from 'ember';

export default Ember.Component.extend({
  //will load the service in file /app/services/shopping-cart.js
  shoppingCart: Ember.inject.service()
});

Another way to inject a service is to provide the name of the service as the argument.

import Ember from 'ember';

export default Ember.Component.extend({
  //will load the service in file /app/services/shopping-cart.js
  cart: Ember.inject.service('shopping-cart')
});

This injects the shopping cart service into the component and makes it available as the cart property.

Sometimes a service may or may not exist, like when an initializer conditionally registers a service. Since normal injection will throw an error if the service doesn't exist, you must look up the service using Ember's getOwner instead.

import Ember from 'ember';

export default Ember.Component.extend({
  //will load the service in file /app/services/shopping-cart.js
  cart: Ember.computed(function() {
    return Ember.getOwner(this).lookup('service:shopping-cart');
  })
});

Injected properties are lazy loaded; meaning the service will not be instantiated until the property is explicitly called. Therefore you need to access services in your component using the get function otherwise you might get an undefined.

Once loaded, a service will persist until the application exits.

Below we add a remove action to the cart-contents component. Notice that below we access the cart service with a call tothis.get.

import Ember from 'ember';

export default Ember.Component.extend({
  cart: Ember.inject.service('shopping-cart'),

  actions: {
    remove(item) {
      this.get('cart').remove(item);
    }
  }
});

Once injected into a component, a service can also be used in the template. Note cart being used below to get data from the cart.

<ul>
  {{#each cart.items as |item|}}
    <li>
      {{item.name}}
      <button {{action "remove" item}}>Remove</button>
    </li>
  {{/each}}
</ul>