Backbone.Subviews

A minimalist view mixin for creating and managing subviews in your Backbone.js applications.

This plugin is designed to manage a fixed number of subviews. If you are looking for a plugin to manage a dynamic number of subviews (i.e. an ordered array of subviews, or a "collection" of subviews), please see Backbone.CollectionView.

Benefits

• Use a clear and consistent syntax to insert subviews in your templates: <div data-subview="mySubview"></div>
• Then access subviews via the automatically populated subviews hash: this.subviews.mySubview
• Can be mixed into any view class, including the base views in Marionette, LayoutManager, etc.
• When a parent view is re-rendered, existing subview objects are reused (state is preserved).
• Automatically cleans up subviews by calling their remove method when parent view is removed.
• Works seamlessly with Backbone.Courier to bubble subview events to parent views.
• Makes it easy to reuse small views, especially if you organize your assets into bundles.

Usage

In your template for MyView, insert a subview named "mySubview" by inserting a div element with a data-subview attribute:

<script type='text/template' id="MyItemViewTemplate">
	<h1>This is my item view template</h1>

	<div data-subview="mySubview"></div>
</script>

Now in MyItemView.js:

MyItemViewClass = Backbone.View.extend( {
	initialize : function() {
		// add backbone.subview functionality to this view
		Backbone.Subviews.add( this );
	},

	subviewCreators : {
		"mySubview" : function() {
			var options = {};

			// do any logic required to create initialization options, etc.,
			// then instantiate and return new subview object
			return new MySubviewClass( options );
		}
	},

	render : function( data ) {
		// render funciton is just like normal.. nothing new here
		var templateFunction = _.template( $( "#MyItemViewTemplate" ).html() );
		this.$el.html( templateFunction( data ) );

		// after we are done rendering, our subviews will automatically be rendered in order
	},

	_onSubviewsRendered : function() {
		// this method (if it exists) is called after subviews are finished rendering.
		// anytime after subviews are rendered, you can find the subviews in the `subviews` hash

		this.listenTo( this.subviews.mySubview, "highlighted", this._mySubview_onHighlighted );
	},

	...
} );

Details

To insert a subview, just put <div data-subview="[subviewName]"></div> in the appropriate place in the parent view's template, where [subviewName] is the name of the subview. This "placeholder" div will be completely replaced with the subview's DOM element.

Then include an entry for the subview in the subviewCreators hash. The key of each entry is this hash is a subview's name, and the value is a function that should create and return the new subview object.

After the parent view's render function is finished, the subviews will automatically be created and rendered (in the order their placeholder divs appear inside the parent view). Once all subviews have been created and rendered, the parent view's _onSubviewsRendered method is called (if one exists), in which you can execute any additional rendering logic that depends on subviews having already been rendered.

When a parent view is re-rendered, its subviews will be re-rendered (their render function will be called), but the subview objects will remain the same - they will not be replaced with completely new view objects. As a result any state information that the subview objects contain will be preserved.

A parent view will automatically call remove on all its subviews when its remove method is called.

Usage with Backbone.Courier

Backbone.Subviews fits together with Backbone.Courier. By default Backbone.Courier expects subviews to be stored in the subview hash, which is exactly where Backbone.Subviews puts them. So right away you can use subviews in Backbone.Courier's onMessages and passMessages hashes. For example:

MyItemViewClass = Backbone.View.extend( {
	initialize : function() {
		// add backbone.subview and backbone.courier functionality to this view
		Backbone.Subviews.add( this );
		Backbone.Courier.add( this );
	},

	subviewCreators : {
		"mySubview" : function() {
			return new MySubviewClass();
		}
	},

	// respond to the "highlighted" message from
	// "mySubview" by calling _mySubview_onHighlighted
	onMessages {
		"highlighted mySubview" : "_mySubview_onHighlighted"
	},

	...
} );

Usage with template helpers

To further simplify the syntax for inserting subviews in your templates, add a global template helper to your template language of choice. For example, with underscore.js templates, the underscore-template-helpers mixin can be used to support this syntax:

<script type='text/template' id="MyItemViewTemplate">
	<h1>This is my item view template</h1>

	<%= subview( "mySubview" ) %>
</script>

Just add the underscore-template-helpers mixin to your project and then declare the subview global template helper:

_.addTemplateHelpers( {
	subview : function( subviewName ) {
		return "<div data-subview='" + subviewName + "'></div>";
	}
} );