Class Application

public
import Application from '@ember/application';

An instance of Ember.Application is the starting point for every Ember application. It helps to instantiate, initialize and coordinate the many objects that make up your app.

Each Ember app has one and only one Ember.Application object. In fact, the very first thing you should do in your application is create the instance:

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window.App = Ember.Application.create();

Typically, the application object is the only global variable. All other classes in your app should be properties on the Ember.Application instance, which highlights its first role: a global namespace.

For example, if you define a view class, it might look like this:

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App.MyView = Ember.View.extend();

By default, calling Ember.Application.create() will automatically initialize your application by calling the Ember.Application.initialize() method. If you need to delay initialization, you can call your app's deferReadiness() method. When you are ready for your app to be initialized, call its advanceReadiness() method.

You can define a ready method on the Ember.Application instance, which will be run by Ember when the application is initialized.

Because Ember.Application inherits from Ember.Namespace, any classes you create will have useful string representations when calling toString(). See the Ember.Namespace documentation for more information.

While you can think of your Ember.Application as a container that holds the other classes in your application, there are several other responsibilities going on under-the-hood that you may want to understand.

Event Delegation

Ember uses a technique called event delegation. This allows the framework to set up a global, shared event listener instead of requiring each view to do it manually. For example, instead of each view registering its own mousedown listener on its associated element, Ember sets up a mousedown listener on the body.

If a mousedown event occurs, Ember will look at the target of the event and start walking up the DOM node tree, finding corresponding views and invoking their mouseDown method as it goes.

Ember.Application has a number of default events that it listens for, as well as a mapping from lowercase events to camel-cased view method names. For example, the keypress event causes the keyPress method on the view to be called, the dblclick event causes doubleClick to be called, and so on.

If there is a bubbling browser event that Ember does not listen for by default, you can specify custom events and their corresponding view method names by setting the application's customEvents property:

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let App = Ember.Application.create({
  customEvents: {
    // add support for the paste event
    paste: 'paste'
  }
});

To prevent Ember from setting up a listener for a default event, specify the event name with a null value in the customEvents property:

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let App = Ember.Application.create({
  customEvents: {
    // prevent listeners for mouseenter/mouseleave events
    mouseenter: null,
    mouseleave: null
  }
});

By default, the application sets up these event listeners on the document body. However, in cases where you are embedding an Ember application inside an existing page, you may want it to set up the listeners on an element inside the body.

For example, if only events inside a DOM element with the ID of ember-app should be delegated, set your application's rootElement property:

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let App = Ember.Application.create({
  rootElement: '#ember-app'
});

The rootElement can be either a DOM element or a jQuery-compatible selector string. Note that views appended to the DOM outside the root element will not receive events. If you specify a custom root element, make sure you only append views inside it!

To learn more about the events Ember components use, see components/handling-events.

Initializers

Libraries on top of Ember can add initializers, like so:

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Ember.Application.initializer({
  name: 'api-adapter',

  initialize: function(application) {
    application.register('api-adapter:main', ApiAdapter);
  }
});

Initializers provide an opportunity to access the internal registry, which organizes the different components of an Ember application. Additionally they provide a chance to access the instantiated application. Beyond being used for libraries, initializers are also a great way to organize dependency injection or setup in your own application.

Routing

In addition to creating your application's router, Ember.Application is also responsible for telling the router when to start routing. Transitions between routes can be logged with the LOG_TRANSITIONS flag, and more detailed intra-transition logging can be logged with the LOG_TRANSITIONS_INTERNAL flag:

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let App = Ember.Application.create({
  LOG_TRANSITIONS: true, // basic logging of successful transitions
  LOG_TRANSITIONS_INTERNAL: true // detailed logging of all routing steps
});

By default, the router will begin trying to translate the current URL into application state once the browser emits the DOMContentReady event. If you need to defer routing, you can call the application's deferReadiness() method. Once routing can begin, call the advanceReadiness() method.

If there is any setup required before routing begins, you can implement a ready() method on your app that will be invoked immediately before routing begins.

Show:

Call advanceReadiness after any asynchronous setup logic has completed. Each call to deferReadiness must be matched by a call to advanceReadiness or the application will never become ready and routing will not begin.

Use this to defer readiness until some condition is true.

Example:

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let App = Ember.Application.create();

App.deferReadiness();

// Ember.$ is a reference to the jQuery object/function
Ember.$.getJSON('/auth-token', function(token) {
  App.token = token;
  App.advanceReadiness();
});

This allows you to perform asynchronous setup logic and defer booting your application until the setup has finished.

However, if the setup requires a loading UI, it might be better to use the router for this purpose.

fullName
String
returns
Boolean

Check if a factory is registered.

initializer
Object

The goal of initializers should be to register dependencies and injections. This phase runs once. Because these initializers may load code, they are allowed to defer application readiness and advance it. If you need to access the container or store you should use an InstanceInitializer that will be run after all initializers and therefore after all code is loaded and the app is ready.

Initializer receives an object which has the following attributes: name, before, after, initialize. The only required attribute is initialize, all others are optional.

  • name allows you to specify under which name the initializer is registered. This must be a unique name, as trying to register two initializers with the same name will result in an error.
initializer.js
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import { debug } from '@ember/debug';

export function initialize() {
  debug('Running namedInitializer!');
}

export default {
  name: 'named-initializer',
  initialize
};
  • before and after are used to ensure that this initializer is ran prior or after the one identified by the value. This value can be a single string or an array of strings, referencing the name of other initializers.

An example of ordering initializers, we create an initializer named first:

app/initializer/first.js
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import { debug } from '@ember/debug';

export function initialize() {
  debug('First initializer!');
}

export default {
  name: 'first',
  initialize
};
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// DEBUG: First initializer!

We add another initializer named second, specifying that it should run after the initializer named first:

app/initializer/second.js
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import { debug } from '@ember/debug';

export function initialize() {
  debug('Second initializer!');
}

export default {
  name: 'second',
  after: 'first',
  initialize
};
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// DEBUG: First initializer!
// DEBUG: Second initializer!

Afterwards we add a further initializer named pre, this time specifying that it should run before the initializer named first:

app/initializer/pre.js
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import { debug } from '@ember/debug';

export function initialize() {
  debug('Pre initializer!');
}

export default {
  name: 'pre',
  before: 'first',
  initialize
};
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// DEBUG: Pre initializer!
// DEBUG: First initializer!
// DEBUG: Second initializer!

Finally we add an initializer named post, specifying it should run after both the first and the second initializers:

app/initializer/post.js
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import { debug } from '@ember/debug';

export function initialize() {
  debug('Post initializer!');
}

export default {
  name: 'post',
  after: ['first', 'second'],
  initialize
};
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// DEBUG: Pre initializer!
// DEBUG: First initializer!
// DEBUG: Second initializer!
// DEBUG: Post initializer!
  • initialize is a callback function that receives one argument, application, on which you can operate.

Example of using application to register an adapter:

adapter.js
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import ApiAdapter from '../utils/api-adapter';

export function initialize(application) {
  application.register('api-adapter:main', ApiAdapter);
}

export default {
  name: 'post',
  after: ['first', 'second'],
  initialize
};
factoryNameOrType
String
property
String
injectionName
String

Define a dependency injection onto a specific factory or all factories of a type.

When Ember instantiates a controller, view, or other framework component it can attach a dependency to that component. This is often used to provide services to a set of framework components.

An example of providing a session object to all controllers:

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let App = Ember.Application.create();
let Session = Ember.Object.extend({ isAuthenticated: false });

// A factory must be registered before it can be injected
App.register('session:main', Session);

// Inject 'session:main' onto all factories of the type 'controller'
// with the name 'session'
App.inject('controller', 'session', 'session:main');

App.IndexController = Ember.Controller.extend({
  isLoggedIn: Ember.computed.alias('session.isAuthenticated')
});

Injections can also be performed on specific factories.

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App.inject(<full_name or type>, <property name>, <full_name>)
App.inject('route', 'source', 'source:main')
App.inject('route:application', 'email', 'model:email')

It is important to note that injections can only be performed on classes that are instantiated by Ember itself. Instantiating a class directly (via create or new) bypasses the dependency injection system.

instanceInitializer

Instance initializers run after all initializers have run. Because instance initializers run after the app is fully set up. We have access to the store, container, and other items. However, these initializers run after code has loaded and are not allowed to defer readiness.

Instance initializer receives an object which has the following attributes: name, before, after, initialize. The only required attribute is initialize, all others are optional.

  • name allows you to specify under which name the instanceInitializer is registered. This must be a unique name, as trying to register two instanceInitializer with the same name will result in an error.
initializer.js
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import { debug } from '@ember/debug';

export function initialize() {
  debug('Running named-instance-initializer!');
}

export default {
  name: 'named-instance-initializer',
  initialize
};
  • before and after are used to ensure that this initializer is ran prior or after the one identified by the value. This value can be a single string or an array of strings, referencing the name of other initializers.

  • See Ember.Application.initializer for discussion on the usage of before and after.

Example instanceInitializer to preload data into the store.

data.js
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import $ from 'jquery';

export function initialize(application) {
    var userConfig, userConfigEncoded, store;
    // We have a HTML escaped JSON representation of the user's basic
    // configuration generated server side and stored in the DOM of the main
    // index.html file. This allows the app to have access to a set of data
    // without making any additional remote calls. Good for basic data that is
    // needed for immediate rendering of the page. Keep in mind, this data,
    // like all local models and data can be manipulated by the user, so it
    // should not be relied upon for security or authorization.

    // Grab the encoded data from the meta tag
    userConfigEncoded = $('head meta[name=app-user-config]').attr('content');

    // Unescape the text, then parse the resulting JSON into a real object
    userConfig = JSON.parse(unescape(userConfigEncoded));

    // Lookup the store
    store = application.lookup('service:store');

    // Push the encoded JSON into the store
    store.pushPayload(userConfig);
}

export default {
  name: 'named-instance-initializer',
  initialize
};
fullName
String
type:name (e.g., 'model:user')
factory
Function
(e.g., App.Person)
options
Object
(optional) disable instantiation or singleton usage

Registers a factory that can be used for dependency injection (with inject) or for service lookup. Each factory is registered with a full name including two parts: type:name.

A simple example:

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let App = Ember.Application.create();

App.Orange = Ember.Object.extend();
App.register('fruit:favorite', App.Orange);

Ember will resolve factories from the App namespace automatically. For example App.CarsController will be discovered and returned if an application requests controller:cars.

An example of registering a controller with a non-standard name:

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let App = Ember.Application.create();
let Session = Ember.Controller.extend();

App.register('controller:session', Session);

// The Session controller can now be treated like a normal controller,
// despite its non-standard name.
App.ApplicationController = Ember.Controller.extend({
  needs: ['session']
});

Registered factories are instantiated by having create called on them. Additionally they are singletons, each time they are looked up they return the same instance.

Some examples modifying that default behavior:

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let App = Ember.Application.create();

App.Person = Ember.Object.extend();
App.Orange = Ember.Object.extend();
App.Email = Ember.Object.extend();
App.session = Ember.Object.create();

App.register('model:user', App.Person, { singleton: false });
App.register('fruit:favorite', App.Orange);
App.register('communication:main', App.Email, { singleton: false });
App.register('session', App.session, { instantiate: false });
fullName
String
options
Object

Register options for a particular factory.

type
String
options
Object

Allow registering options for all factories of a type.

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let App = Ember.Application.create();
let appInstance = App.buildInstance();

// if all of type `connection` must not be singletons
appInstance.registerOptionsForType('connection', { singleton: false });

appInstance.register('connection:twitter', TwitterConnection);
appInstance.register('connection:facebook', FacebookConnection);

let twitter = appInstance.lookup('connection:twitter');
let twitter2 = appInstance.lookup('connection:twitter');

twitter === twitter2; // => false

let facebook = appInstance.lookup('connection:facebook');
let facebook2 = appInstance.lookup('connection:facebook');

facebook === facebook2; // => false
fullName
String
optionName
String
returns
Object
options

Return a specific registered option for a particular factory.

fullName
String
returns
Object
options

Return registered options for a particular factory.

type
String
returns
Object
options

Return the registered options for all factories of a type.

Reset the application. This is typically used only in tests. It cleans up the application in the following order:

  1. Deactivate existing routes
  2. Destroy all objects in the container
  3. Create a new application container
  4. Re-route to the existing url

Typical Example:

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let App;

run(function() {
  App = Ember.Application.create();
});

module('acceptance test', {
  setup: function() {
    App.reset();
  }
});

test('first test', function() {
  // App is freshly reset
});

test('second test', function() {
  // App is again freshly reset
});

Advanced Example:

Occasionally you may want to prevent the app from initializing during setup. This could enable extra configuration, or enable asserting prior to the app becoming ready.

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let App;

run(function() {
  App = Ember.Application.create();
});

module('acceptance test', {
  setup: function() {
    run(function() {
      App.reset();
      App.deferReadiness();
    });
  }
});

test('first test', function() {
  ok(true, 'something before app is initialized');

  run(function() {
    App.advanceReadiness();
  });

  ok(true, 'something after app is initialized');
});
fullName
String
returns
Function
fullName's factory

Given a fullName return the corresponding factory.

fullName
String

Unregister a factory.

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let App = Ember.Application.create();
let User = Ember.Object.extend();
App.register('model:user', User);

App.resolveRegistration('model:user').create() instanceof User //=> true

App.unregister('model:user')
App.resolveRegistration('model:user') === undefined //=> true
url
String
The initial URL to navigate to
options
ApplicationInstance.BootOptions
returns
Promise<ApplicationInstance, Error>

Boot a new instance of Ember.ApplicationInstance for the current application and navigate it to the given url. Returns a Promise that resolves with the instance when the initial routing and rendering is complete, or rejects with any error that occurred during the boot process.

When autoboot is disabled, calling visit would first cause the application to boot, which runs the application initializers.

This method also takes a hash of boot-time configuration options for customizing the instance's behavior. See the documentation on Ember.ApplicationInstance.BootOptions for details.

Ember.ApplicationInstance.BootOptions is an interface class that exists purely to document the available options; you do not need to construct it manually. Simply pass a regular JavaScript object containing of the desired options:

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MyApp.visit("/", { location: "none", rootElement: "#container" });

Supported Scenarios

While the BootOptions class exposes a large number of knobs, not all combinations of them are valid; certain incompatible combinations might result in unexpected behavior.

For example, booting the instance in the full browser environment while specifying a foreign document object (e.g. { isBrowser: true, document: iframe.contentDocument }) does not work correctly today, largely due to Ember's jQuery dependency.

Currently, there are three officially supported scenarios/configurations. Usages outside of these scenarios are not guaranteed to work, but please feel free to file bug reports documenting your experience and any issues you encountered to help expand support.

Browser Applications (Manual Boot)

The setup is largely similar to how Ember works out-of-the-box. Normally, Ember will boot a default instance for your Application on "DOM ready". However, you can customize this behavior by disabling autoboot.

For example, this allows you to render a miniture demo of your application into a specific area on your marketing website:

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import MyApp from 'my-app';

$(function() {
  let App = MyApp.create({ autoboot: false });

  let options = {
    // Override the router's location adapter to prevent it from updating
    // the URL in the address bar
    location: 'none',

    // Override the default `rootElement` on the app to render into a
    // specific `div` on the page
    rootElement: '#demo'
  };

  // Start the app at the special demo URL
  App.visit('/demo', options);
});

Or perhaps you might want to boot two instances of your app on the same page for a split-screen multiplayer experience:

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import MyApp from 'my-app';

$(function() {
  let App = MyApp.create({ autoboot: false });

  let sessionId = MyApp.generateSessionID();

  let player1 = App.visit(`/matches/join?name=Player+1&session=${sessionId}`, { rootElement: '#left', location: 'none' });
  let player2 = App.visit(`/matches/join?name=Player+2&session=${sessionId}`, { rootElement: '#right', location: 'none' });

  Promise.all([player1, player2]).then(() => {
    // Both apps have completed the initial render
    $('#loading').fadeOut();
  });
});

Do note that each app instance maintains their own registry/container, so they will run in complete isolation by default.

Server-Side Rendering (also known as FastBoot)

This setup allows you to run your Ember app in a server environment using Node.js and render its content into static HTML for SEO purposes.

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const HTMLSerializer = new SimpleDOM.HTMLSerializer(SimpleDOM.voidMap);

function renderURL(url) {
  let dom = new SimpleDOM.Document();
  let rootElement = dom.body;
  let options = { isBrowser: false, document: dom, rootElement: rootElement };

  return MyApp.visit(options).then(instance => {
    try {
      return HTMLSerializer.serialize(rootElement.firstChild);
    } finally {
      instance.destroy();
    }
  });
}

In this scenario, because Ember does not have access to a global document object in the Node.js environment, you must provide one explicitly. In practice, in the non-browser environment, the stand-in document object only needs to implement a limited subset of the full DOM API. The SimpleDOM library is known to work.

Since there is no access to jQuery in the non-browser environment, you must also specify a DOM Element object in the same document for the rootElement option (as opposed to a selector string like "body").

See the documentation on the isBrowser, document and rootElement properties on Ember.ApplicationInstance.BootOptions for details.

Server-Side Resource Discovery

This setup allows you to run the routing layer of your Ember app in a server environment using Node.js and completely disable rendering. This allows you to simulate and discover the resources (i.e. AJAX requests) needed to fulfill a given request and eagerly "push" these resources to the client.

service.js
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import BrowserNetworkService from 'app/services/network/browser';
import NodeNetworkService from 'app/services/network/node';

// Inject a (hypothetical) service for abstracting all AJAX calls and use
// the appropriate implementation on the client/server. This also allows the
// server to log all the AJAX calls made during a particular request and use
// that for resource-discovery purpose.

export function initialize(application) {
  if (window) { // browser
    application.register('service:network', BrowserNetworkService);
  } else { // node
    application.register('service:network', NodeNetworkService);
  }

  application.inject('route', 'network', 'service:network');
};

export default {
  name: 'network-service',
  initialize: initialize
};
app/routes/post.js
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import Route from '@ember/routing/route';

// An example of how the (hypothetical) service is used in routes.

export default Route.extend({
  model(params) {
    return this.network.fetch(`/api/posts/${params.post_id}.json`);
  },

  afterModel(post) {
    if (post.isExternalContent) {
      return this.network.fetch(`/api/external/?url=${post.externalURL}`);
    } else {
      return post;
    }
  }
});
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// Finally, put all the pieces together

function discoverResourcesFor(url) {
  return MyApp.visit(url, { isBrowser: false, shouldRender: false }).then(instance => {
    let networkService = instance.lookup('service:network');
    return networkService.requests; // => { "/api/posts/123.json": "..." }
  });
}