title: Mongoose query returning arrays as undefined
body: <p>I currently have a mongoose model that I am saving multiple IDs as an array.</p>
  
  <pre><code>var map = new Schema ({
      "AdminID" : [{type: mongoose.Schema.Types.ObjectId, required: false }],
      "AdminKeys" : [{type: mongoose.Schema.Types.ObjectId, required: false }]
  });
  </code></pre>
  
  <p>When I make a query through the mongo shell, I can see that there are some values in the AdminKeys array.</p>
  
  <pre><code>"_id" : ObjectId("584101b5b2483a57256bdf16"),
  "AdminID" : [ ],
  "AdminKeys" : [
          ObjectId("583b5f0b9a64391584e4b4ad")
  ]
  </code></pre>
  
  <p>However, in my controller, when I try and do</p>
  
  <pre><code>Map.findOne({_id: ObjectId('584101b5b2483a57256bdf16')}, 
  {_id : 0, AdminID: 1, AdminKeys: 1 } (err, map) =&gt; {
  
        if (err) {
          console.log(err);
          return;
        }
        console.log(map);
  }
  </code></pre>
  
  <p>I am left with undefined array fields and cannot access any of the values within my AdminKeys array.</p>
  
  <pre><code>_doc: 
       { AdminID: undefined,
         AdminKey: undefined },
  '$__original_save': [Function],
  </code></pre>
  
  <p>If someone would be so kind to help me understand what is going on and a work around, It would be much appreciated.</p>