title: Using Meteor.ObjectID as a type in SimpleSchema
body: <p>I have two Schemas using SimpleSchema - say Schema1 and Schema2. I want to reference the internal ObjectId (_id) from Schema1 in Schema2. How do I go about doing this?</p>
  
  <p>Schema1 looks like this:</p>
  
  <pre><code>Schema1 = new SimpleSchema({
      aitem: {
          type: String
      },
      anitem: {
          type: String
      }
  });
  </code></pre>
  
  <p>Schema2 looks like this:</p>
  
  <pre><code>Schema2 = new SimpleSchema({
      aaitem: {
          type: String
      },
      aanitem: {
          type: String
      },
      refItem: {
          type: Mongo.ObjectID
      }
  });
  </code></pre>
  
  <p>When I try an insert in Meteor it says cannot validate ObjectID</p>