How to access a composite view from an item view instance in Backbone Marionette

Question

If you want to access data from the parent CompositeView you can do a number of different things.

1. Either pass that data directly to the ItemView through the itemViewOptions helper function on the CompositeView. Note: This option has changed to childViewOptions in Marionette 2.

2. Invoke a method directly on all of the children view from the CompositeView and pass whatever you want into that method.

3. Trigger an event on or listened for by the ItemView.

None of these options are directly accessing the parent view from the child but should do what you want. Below is code for how to use each of these approaches to pass the CompositeView's model to the children view.

// Pass model into ItemView on init
var MyItemView = Backbone.Marionette.ItemView.extend({
  initialize : function (options) {
    this.parentsModel = options.parentsModel;
  }
});
var MyCompView = Backbone.Marionette.CompositeView.extend({
  itemViewOptions : function () { return { parentsModel: this.model }; }
  itemView : MyItemView
});


// Invoke function on ItemView, passing data in
var MyItemView = Backbone.Marionette.ItemView.extend({
  doSomethingWithParent : function (parentModel) {
    // do cool thing with parentModel
  }
});
var MyCompView = Backbone.Marionette.CompositeView.extend({
  itemView : MyItemView,
  onRender : function () {
    this.children.call("doSomethingWithParent", this.model);
  }
});


// Trigger event that ItemView knows about
var MyItemView = Backbone.Marionette.ItemView.extend({
  initialize : function () {
    this.listenTo(this, "special:event", function (parentModel) {
      // Do cool things
    });
  }
});
var MyCompView = Backbone.Marionette.CompositeView.extend({
  itemView : MyItemView,
  onRender : function () {
    this.children.each(_.bind(function (childView) {
      childView.trigger("special:event", this.model);
     }, this));
  }
});

I didn't answer the question. But changing the approach works. Instead of trying to access the 'parent' Composite View from the Item View I access the Item View from the Composite View:

https://github.com/marionettejs/backbone.marionette/blob/master/docs/marionette.collectionview.md#onbeforeitemadded-callback

I can modify the model of the current item view (based on a value in the model of the Composite View).

Thought I'd share how Andrew Hubbs suggestion helped me. I was trying to display a parent model property inline with my item template. I used Marionette's templateHelpers property to do this in combination with one of Andrew's suggestions.

I tried to keep the example brief:

Example Composite template - myView Template:

<h1>Page {{name}}</h1>
<h6>Children</h6>
<ul></ul>

Example item template - myItemTemplate:

{{name}} is child of: {{getParentName}}

Views:

App.module( 'App.View', function( View ){

    View.MyItemView = Marionette.ItemView.extend({

        initialize: function( options ) {
            this.parentModel = options.parentModel;
        },

        template: myItemTemplate,

        tagName: 'li',

        templateHelpers: function() {

            var view = this;

            return {
                // Called by item template, returns parent model 'name' property.
                getParentName: function() {
                    return view.parentModel.get('name');
                }

            };
        }

    });

    View.MyView = Marionette.CompositeView.extend({

        template: myViewTemplate,

        itemView: View.MyItemView,

        itemViewContainer: 'ul',

        itemViewOptions: function() {

            return { parentModel: this.model };

        }

    });

});

An example of how this would be implemented:

// example of how implementation
// parent model has an attribute called 'children', which is a collection of models
var children = parent.get('children');

var view = new App.View.MyView( { model: parent, collection: children } );

App.mainRegion.show( view );