There's no built-in garbage collection for Backbone’s event bindings, and forgetting to unbind can cause bugs and memory leaks.

Backbone Support currently provides two utility classes, SwappingRouter and CompositeView, that introduce a leave() function, which unbinds and cleans up the view. They should be used where views are instantiated (in Router instances and in composite views).

Inspired by our projects and the Backbone.js on Rails book: http://workshops.thoughtbot.com/backbone-js-on-rails

The book contains complete instructions and in-depth coverage of the internals of CompositeView and SwappingRouter, and an example application that shows their usage.

SwappingRouter

A Router subclass the provides a standard way to swap one view for another.

This introduces a convention that all views have a leave() function, responsible for unbinding and cleaning up the view. And the convention that all actions underneath the same Router share the same root element, and define it as el on the router. It also requires that all view's render method returns the view itself (a fairly standard backbone convention).

Now, a SwappingRouter can take advantage of the leave() function, and clean up any existing views before swapping to a new one. It swaps into a new view by rendering that view into its own el:

swap: function(newView) {
  if (this.currentView && this.currentView.leave) {
    this.currentView.leave();
  }

  this.currentView = newView;
  $(this.el).empty().append(this.currentView.render().el);
}

An example SwappingRouter would look as follows:

Trajectory.Routers.Stories = Support.SwappingRouter.extend({
  initialize: function(options) {
    this.el = $("div.primary_content");
  },
  routes: {
    "stories": "index",
    "stories/new": "newStory"
  }
  index: function(story_id) {
    var view = new Trajectory.Views.StoriesIndex();
    this.swap(view);
  },
  newStory: function() {
    var view = new Trajectory.Views.StoryNew({ model: new Story() });
    this.swap(view);
  }
}

CompositeView

CompositeView provides a convention for a parent view that has one or more child views.

This introduces a convention that all views have a leave() function, responsible for unbinding and cleaning up the view.

CompositeView provides methods for adding and removing children from the parent view.

CompositeView maintains an array of its immediate children as this.children. With this reference in place, a parent view's leave() method can invoke leave() on its children, ensuring that an entire tree of composed views is cleaned up properly.

For child views that can dismiss themselves, such as dialog boxes, children maintain a back-reference at this.parent. This is used to reach up and call this.parent.removeChild(this) for these self-dismissing views.

Dependencies

You'll need these, but chances are you already have them in your app:

• jQuery or Zepto
• Underscore
• Backbone

Development

First:

bundle

While TDD'ing:

bundle exec rake jasmine

To not open tests a browser window:

bundle exec rake jasmine:ci

Installation

The recommended usage is with Rails 3.1.

With Rails 3.1

Add the gem to your Gemfile

gem "backbone-support"

And then bundle install

In your application.js, or in whatever file your backbone.js assets are required in, add the following:

//= require backbone-support

This should be above any usage of SwappingController or SwappingRouter, but below the inclusion of Backbone.js, Underscore, and jQuery.

If you do not wish to include all of backbone-support, you can include individual pieces. First, require the main support file:

//= require backbone-support/support

Then require the individual assets you wish to use:

//= require backbone-support/swapping_router
//= require backbone-support/composite_view

With Jammit

First off:

rails plugin install [email protected]:thoughtbot/backbone-support.git

In your config/application.rb:

config.middleware.use Rack::Static,
                      :urls => ['/vendor/plugins/backbone-support/lib/assets/javascripts']

And in your config/assets.yml:

javascripts:
  common:
    - public/javascripts/vendor/underscore.js
    - public/javascripts/vendor/backbone.js
    - vendor/plugins/backbone-support/lib/assets/**/*.js

If you have evergreen tests, you will need to change your require statements since these files live in vendor/. Change config/evergreen.rb to be this:

Evergreen.configure do |config|
  config.public_dir = '.'
end

Your individual specs will then need the full root path in require. For example:

requirePublic = function(path) {
  require("/public/javascripts/" + path);
};

requirePublic("vendor/underscore.js");
requirePublic("vendor/backbone.js");

require("/vendor/plugins/backbone-support/lib/assets/javascripts/backbone-support.js");
require("/vendor/plugins/backbone-support/lib/assets/javascripts/backbone-support/composite_view.js");
require("/vendor/plugins/backbone-support/lib/assets/javascripts/backbone-support/swapping_router.js");

License

Copyright 2011 thoughtbot. Please check LICENSE for more details.