title: Unable to return _id of a subdocument using mongoosejs
body: <pre><code>[
  {
      "_id": "58b89de6a480ce48c8f3742d",
      "name": "Core Site",
      "version": "1.0.0",
      "author": "Jane Doe",
      "vendor": "Online Banking",
      "steps": [
          {
              "name": "Step 1: Fun Stuff",
              "dependencies": "1,2,3,4",
              "resource": "TS",
              "weight": 0
          },
          {
              "name": "Step 2: Weird Stuff",
              "dependencies": "3,4",
              "resource": "PS",
              "weight": 1
          }
      ]
  },
  {
      "_id": "58b8a22097fbe41746827ac7",
      "name": "Online Statements",
      "version": "1.0.0",
      "author": "John Doe",
      "vendor": "Online Banking",
      "steps": [
          {
              "name": "Step 1: Fun Stuff",
              "dependencies": "1,2,3,4",
              "resource": "TS",
              "weight": 0
          }
      ]
  }]
  </code></pre>
  
  <p>I have saved this information into a MongoDB but when I try to get this information the sub-document "Steps" does not include the _id that I can see using Robomongo.</p>
  
  <p>My schema is as follows:</p>
  
  <pre><code>    // grab the things we need
  var mongoose = require('mongoose');
  var Schema = mongoose.Schema;
  
  var stepSchema = new Schema({
    name: { type: String, required: true},
    dependencies: String,
    resource: String,
    weight: Number
  })
  
  // create a schema
  var sopSchema = new Schema({
    name: { type: String, required: true, unique: true },
    version: String,
    author: String,
    vendor: String,
    steps: [stepSchema]
  });
  
  
  
  // the schema is useless so far
  // we need to create a model using it
  var Sop = mongoose.model('Sop', sopSchema);
  
  // make this available to our users in our Node applications
  module.exports = Sop;
  </code></pre>
  
  <p>My end goal is to check if the step is already included and update it when making a change on the front end.  So i wanted to get this reference to ensure i have the right subdocument.</p>
  
  <p>My get statement is as follows in my nodejs server.</p>
  
  <pre><code>router.route('/sops')
      .get(function(req, res) {
          Sop.find(function(err, sops) {
              if (err)
                  res.send(err);
  
                  var subdoc = sops[0].steps[0];
                  console.log(subdoc);
              res.json(sops);
      });
  })
  </code></pre>