Unable to access backbone model attributes

Question

I have a board model which has category_id which is representing category parent class i.e. one category has many boards. I have a following ruby model

app/models/board.rb

class Board < ActiveRecord::Base
attr_accessible :description, :name, :open, :members, :category_id
belongs_to :category

end

Only I want to get category object by using category_id (which is accessible) in backbone template label tag. I am getting null in label tag if I access category object.

<div class="myNavigation">
  <nav class="vertical">
    <ul>
      <% boards.each(function (board) { %>  
        <li>
           <% debugger; %>
          <label for="home"><%= board.escape("category_id") %></label>
          <input type="radio" checked="true" name="verticalMenu" id="home" />
          <div>
            
          </div>
        </li>
      <% }); %>
     
    </ul>
  </nav>
</div>

Following is a lot of code, and if some more needed i will post.

backbone model:

app/assets/javascripts/model/board.js

Kanban.Models.Board = Backbone.RelationalModel.extend({

  urlRoot: "/api/boards",

    relations: [{
        type: Backbone.HasMany,
        key: "lists",
        relatedModel: "Kanban.Models.List",
        collectionType: "Kanban.Collections.Lists",
        reverseRelation: {
            key: "board"
        }
    },{
        type: Backbone.HasMany,
        key: "users",
        relatedModel: "Kanban.Models.User",
        collectionType: "Kanban.Collections.Users"
    }]
});

category model:

app/assets/javascripts/model/category.js

Kanban.Models.Category = Backbone.RelationalModel.extend({

  urlRoot: "/categories",

    relations: [{
        type: Backbone.HasMany,
        key: "boards",
        relatedModel: "Kanban.Models.Board",
        collectionType: "Kanban.Collections.Boards",
        reverseRelation: {
            key: "category"
        }
    }]
});

app/views/categories/index.rabl

collection @categories
attributes :id, :title, :description