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Marionette.Application

The Application is a container for the rest of your code. It is recommended
that every Marionette app have at least one instance of Application.

By creating an Application you get three important things:

Note that the Application is undergoing many changes to become more lightweight. While it
still includes many more features beyond what has been listed here, such as a Radio Channel and Regions,
these features are now deprecated. Refer to the relevant sections below to learn what to use
instead of these deprecated features.

Documentation Index

Getting Started

A common pattern in Backbone apps is the following:

var app = {};

The most notable example of this pattern is
DocumentCloud's source. DocumentCloud
is notable because it is the codebase that Backbone was abstracted from. If such a thing as a quintessential Backbone application
existed, then that app would certainly be a candidate.

The pattern of creating a Javascript object is so popular because it provides you with a location to
put the pieces of your application. For instance, attaching a Router to this object is common practice.

Using a raw Javascript object is great, but Marionette provides a light wrapper for a plain Javascript object, which is the
Application. One benefit to using the Application is that it comes with a start method. This can be used to accomplish
tasks before the rest of your application begins. Let's take a quick look at an example:

// Create our Application
var app = new Mn.Application();

// Start history when our application is ready
app.on('start', function() {
  Backbone.history.start();
});

// Load some initial data, and then start our application
loadInitialData().then(app.start);

In the simple example above, we could have just as easily started history after our initial data had loaded. This
pattern becomes more useful as the startup phase of your application becomes more complex.

Initialize

Like other objects in Backbone and Marionette, Applications have an initialize method.
It is called immediately after the Application has been instantiated, and is invoked with
the same arguments that the constructor received.

var app = Marionette.Application.extend({
  initialize: function(options) {
    console.log('My container:', options.container);
  }
});

// Although applications will not do anything
// with a `container` option out-of-the-box, you
// could build an Application Class that does use
// such an option.
var app = new app({container: '#app'});

Application Events

The Application object raises a few events during its lifecycle, using the
Marionette.triggerMethod function. These events
can be used to do additional processing of your application. For example, you
may want to pre-process some data just before initialization happens. Or you may
want to wait until your entire application is initialized to start
Backbone.history.

The events that are currently triggered, are:

MyApp.on("before:start", function(options){
  options.moreData = "Yo dawg, I heard you like options so I put some options in your options!";
});

MyApp.on("start", function(options){
  if (Backbone.history){
    Backbone.history.start();
  }
});

The options parameter is passed through the start method of the application
object (see below).

Starting An Application

Once you have your application configured, you can kick everything off by
calling: MyApp.start(options).

This function takes a single optional parameter. This parameter will be passed
to each of your initializer functions, as well as the initialize events. This
allows you to provide extra configuration for various parts of your app throughout the
initialization sequence.

var options = {
  something: "some value",
  another: "#some-selector"
};

MyApp.start(options);

Application Regions

Warning: deprecated
This feature is deprecated. Instead of using the Application as the root
of your view tree, you should use a Layout View. To scope your Layout View to the entire
document, you could set its el to 'body'. This might look something like the following:

var RootView = Marionette.LayoutView.extend({
  el: 'body'
});

Later, you can attach an instance of the RootView to your Application instance.

app.rootView = new RootView();

Application instances have an API that allow you to manage Regions.
These Regions are typically the means through which your views become attached to the document.

You can create Regions through the addRegions method by passing in an object
literal or a function that returns an object literal.

There are three syntax forms for adding a region to an application object.

jQuery Selector

The first is to specify a jQuery selector as the value of the region
definition. This will create an instance of a Marionette.Region directly,
and assign it to the selector:

MyApp.addRegions({
  someRegion: "#some-div",
  anotherRegion: "#another-div"
});

Custom Region Class

The second is to specify a custom region class, where the region class has
already specified a selector:

var MyCustomRegion = Marionette.Region.extend({
  el: "#foo"
});

MyApp.addRegions(function() {
  return {
    someRegion: MyCustomRegion
  };
});

Custom Region Class And Selector

The third method is to specify a custom region class, and a jQuery selector
for this region instance, using an object literal:

var MyCustomRegion = Marionette.Region.extend({});

MyApp.addRegions({

  someRegion: {
    selector: "#foo",
    regionClass: MyCustomRegion
  },

  anotherRegion: {
    selector: "#bar",
    regionClass: MyCustomRegion
  }

});

Region Options

You can also specify regions per Application instance.

new Marionette.Application({
  regions: {
    fooRegion: '#foo-region'
  }
});

Overriding the default RegionManager

If you need the RegionManager's class chosen dynamically, specify getRegionManager:

Marionette.Application.extend({
  // ...

  getRegionManager: function() {
    // custom logic
    return new MyRegionManager();
  }

This can be useful if you want to attach Application's regions to your own instance of RegionManager.

Get Region By Name

A region can be retrieved by name, using the getRegion method:

var app = new Marionette.Application();
app.addRegions({ r1: "#region1" });

var myRegion = app.getRegion('r1');

Regions are also attached directly to the Application instance, but this is not recommended usage.

Removing Regions

Regions can also be removed with the removeRegion method, passing in
the name of the region to remove as a string value:

MyApp.removeRegion('someRegion');

Removing a region will properly empty it before removing it from the
application object.

For more information on regions, see the region documentation Also, the API that Applications use to
manage regions comes from the RegionManager Class, which is documented over here.

Application.mergeOptions

Merge keys from the options object directly onto the Application instance.

var MyApp = Marionette.Application.extend({
  initialize: function(options) {
    this.mergeOptions(options, ['myOption']);

    console.log('The option is:', this.myOption);
  }
})

More information at mergeOptions

Application.getOption

Retrieve an object's attribute either directly from the object, or from the object's this.options, with this.options taking precedence.

More information getOption

Adding Initializers

Warning: deprecated

This feature is deprecated, and is scheduled to be removed in version 3 of Marionette. Instead
of Initializers, you should use events to manage start-up logic. The start event is an ideal
substitute for Initializers.

If you were relying on the deferred nature of Initializers in your app, you should instead
use Promises. This might look something like the following:

doAsyncThings().then(app.start);

Your application needs to do useful things, like displaying content in your
regions, starting up your routers, and more. To accomplish these tasks and
ensure that your Application is fully configured, you can add initializer
callbacks to the application.

MyApp.addInitializer(function(options){
  // do useful stuff here
  var myView = new MyView({
    model: options.someModel
  });
  MyApp.mainRegion.show(myView);
});

MyApp.addInitializer(function(options){
  new MyAppRouter();
  Backbone.history.start();
});

These callbacks will be executed when you start your application,
and are bound to the application object as the context for
the callback. In other words, this is the MyApp object inside
of the initializer function.

The options argument is passed from the start method (see below).

Initializer callbacks are guaranteed to run, no matter when you
add them to the app object. If you add them before the app is
started, they will run when the start method is called. If you
add them after the app is started, they will run immediately.

The Application Channel

Warning: deprecated

This feature is deprecated, and is scheduled to be removed in the next major release of Marionette.
Instead of accessing Channels through the Application, you should use the Wreqr (or Radio) API.
By default the application's channel is named 'global'. To access this channel, you can use
the following code, depending on whether you're using Wreqr or Radio:

// Wreqr
var globalCh = Backbone.Wreqr.radio.channel('global');

// Radio
var globalCh = Backbone.Radio.channel('global');

Marionette Applications come with a messaging system to facilitate communications within your app.

The messaging system on the Application is the radio channel from Backbone.Wreqr, which is actually comprised of three distinct systems.

Marionette Applications default to the 'global' channel, but the channel can be configured.

var MyApp = new Marionette.Application({ channelName: 'appChannel' });

This section will give a brief overview of the systems; for a more in-depth look you are encouraged to read
the Backbone.Wreqr documentation.

Event Aggregator

The Event Aggregator is available through the vent property. vent is convenient for passively sharing information between
pieces of your application as events occur.

var MyApp = new Marionette.Application();

// Alert the user on the 'minutePassed' event
MyApp.vent.on("minutePassed", function(someData){
  alert("Received", someData);
});

// This will emit an event with the value of window.someData every minute
window.setInterval(function() {
  MyApp.vent.trigger("minutePassed", window.someData);
}, 1000 * 60);

Request Response

Request Response is a means for any component to request information from another component without being tightly coupled. An instance of Request Response is available on the Application as the reqres property.

var MyApp = new Marionette.Application();

// Set up a handler to return a todoList based on type
MyApp.reqres.setHandler("todoList", function(type){
  return this.todoLists[type];
});

// Make the request to get the grocery list
var groceryList = MyApp.reqres.request("todoList", "groceries");

// The request method can also be accessed directly from the application object
var groceryList = MyApp.request("todoList", "groceries");

Commands

Commands are used to make any component tell another component to perform an action without a direct reference to it. A Commands instance is available under the commands property of the Application.

Note that the callback of a command is not meant to return a value.

var MyApp = new Marionette.Application();

MyApp.model = new Backbone.Model();

// Set up the handler to call fetch on the model
MyApp.commands.setHandler("fetchData", function(reset){
  MyApp.model.fetch({reset: reset});
});

// Order that the data be fetched
MyApp.commands.execute("fetchData", true);

// The execute function is also available directly from the application
MyApp.execute("fetchData", true);

Accessing the Application Channel

To access this application channel from other objects within your app you are encouraged to get a handle of the systems
through the Wreqr API instead of the Application instance itself.

// Assuming that we're in some class within your app,
// and that we are using the default 'global' channel
// it is preferable to access the channel like this:
var globalCh = Backbone.Wreqr.radio.channel('global');
globalCh.vent;

// This is discouraged because it assumes the name of your application
window.app.vent;
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