title: Combining 2 Collection in 1 Template Meteor.js
body: <p>I'm trying to make a category system and i cant seem to figure out how to make it work.
  here's a mock js and html to demonstrate what im trying to accomplish</p>
  
  <p>test.js</p>
  
  <pre><code>Categories = new Meteor.Collection('categories');
  Rooms = new Meteor.Collection('rooms');
  
  if (Meteor.isClient) {    
     Template.Category_System.categories = function () {
        return Categories.find({});
     };
     Template.Category_System.rooms = function () {
        return Rooms.find({}); //here i want to return the rooms and users in the Rooms collection but only the rooms that fall under the category and subcategory of the Categories collection
     };
  }
  
  if (Meteor.isServer) {
     Meteor.startup(function () {
          Categories.insert({category:"category1",subcategories:[{subcategory:"subcategory1",rooms:[]},{subcategory:"subcategory2",rooms:[]}]};
          Categories.insert({category:"category2",subcategories:[{subcategory:"subcategory1",rooms:[]},{subcategory:"subcategory2",rooms:[]}]};
  
          Rooms.insert({category:"category1",subcategory:"subcategory1",room:'Room_01',users:[a,b,c]});
          Rooms.insert({category:"category1",subcategory:"subcategory1",room:'Room_02',users:[d,e,f,g,h]});
          Rooms.insert({category:"category1",subcategory:"subcategory2",room:'Room_03',users:[i]}); 
          Rooms.insert({category:"category2",subcategory:"subcategory1",room:'Room_01',users:[j,k]});
          Rooms.insert({category:"category2",subcategory:"subcategory2",room:'Room_02',users:[l,m,n]});
          Rooms.insert({category:"category2",subcategory:"subcategory2",room:'Room_03',users:[o,p,q,r]});               
     });
  }
  </code></pre>
  
  <p>test.html -> just the template</p>
  
  <pre><code>&lt;template name="Category_System"&gt;
     {{#each categories}}
          {{category}}
          {{#each subcategories}}
               {{subcategory}}
               {{#each rooms}}
                    {{room}}{{users}}
               {{/each}}
          {{/each}}
     {{/each}}
  &lt;/template&gt;
  </code></pre>
  
  <p>the outcome i'm trying to achieve</p>
  
  <pre><code>category1
      -subcategory1
           -Room_01 a,b,c
           -Room_02 d,e,f,g,h
      -subcategory2
           -Room_03 i
  category2
      -subcategory1
           -Room_01 j,k
      -subcategory2
           -Room_02 l,m,n
           -Room_03 o,p,q,r
  </code></pre>
  
  <p>thanks in advance</p>