title: How to initialize the selection for rails-select2 in BackboneForms schema?
body: <p>The project uses <a href="https://github.com/rahilsondhi/marionette-rails" rel="nofollow">marionette-rails</a>, <a href="https://github.com/meleyal/backbone-on-rails" rel="nofollow">backbone-on-rails</a>, <a href="https://github.com/argerim/select2-rails" rel="nofollow">select2-rails</a> and this <a href="https://gist.github.com/Integral/5156170" rel="nofollow">port to BackboneForms</a> to provide a multiselect form field. The select options are available to the user. They are retrieved from the collection containing the total list of options:
  </p>
  
  <pre><code>MyApp.module("Products", function(Products, App, Backbone, Marionette, $, _) {
  
    Products.CustomFormView = Products.CustomView.extend({
  
      initialize: function(options) {
        this.model.set("type", "Product");
        Products.EntryView.prototype.initialize.apply(this, arguments);
      },
  
      schemata: function() {
        var products = this.collection.byType("Product");
        var productTypes = products.map(function(product){
          return {
            val: product.id,
            label: product.get("name")
          };
        });
  
        return {
          productBasics: {
            name: {
              type: "Text",
              title: "Name",
              editorAttrs: {
                maxLength: 60,
              }
            },
            type: {
              type: 'Select2',
              title: "Product type",
              options: {
                values: productTypes,
                value: [3, 5],
                initSelection: function (element, callback) {
                  var data = [];
                  $(element.val().split(",")).each(function () {
                    data.push({id: this, text: this});
                  });
                  callback(data);
                }
              },
              editorAttrs: {
                'multiple': 'multiple'
              }
            }
          }
        };
      }
  
    });
  });
  </code></pre>
  
  <p>Do I initialize the <code>value</code> correctly in <code>options.value</code>? How comes <code>initSelection</code> is never called? I copied the function from the documentation - it might be incomplete for my case. None of the products with the IDs <code>3</code> and <code>5</code> is displayed as the selection.</p>