title: Node.js & Mongoose, can't recover _id
body: <p>I'm trying to save a document in my collection and if the save is successful, return the _id of this same document. The problem is I get an undefined value to my _id in both case, either the created model from mongoose or from the callback return. Basically, my only way of getting the _id would be to search the document by one of its properties, and then get the value. This approach isnt what I want, knowing what im currently trying to do should work.</p>
  
  <pre><code>var createTrophy = new Trophy({
      name            : post.name,
      accessCode      : post.password,
      description     : post.description,
      members         : [id]  
    });
  
    Trophy.findOne({name:post.name}, function(err, trophy) {
      if(err){
        console.log('Mongoose: Error: ' + err);
        res.send('Error db query -&gt; ' + err);
      }
      else if(trophy){
        console.log('Trophy ' + trophy.name + ' already existant');
        res.send('Trophy ' + trophy.name + ' already existant');
      }else{  
      createTrophy.save(function(err, doc){
        var uid = createTrophy._id;
        if (err) { 
          console.log('Error in trophy saving:' + err); 
          res.send('Error in trophy saving:' + err);
        }else{ 
          User.findOne({_id:post.id}, function(err, user) {
            if(err){
              console.log('Mongoose: Error: ' + err);
              res.send('Error db query -&gt; ' + err);
            }
            else if(user){
              console.log(doc._id + ' ' + uid);
              user.trophyLink = doc._id;
              res.send(user);
              //user.save(function(err){
              //   if(err){res.send('Couldnt update trophy of profile');} 
              //});
            }
            else{
              console.log('User id Inexistant'); 
              res.send('User id Inexistant');
            }
          });
        }
      });
      }  
    });
  });
  </code></pre>
  
  <p>The Schema</p>
  
  <pre><code> var Trophy = new Schema({
          _id             : ObjectId,
          name            : String,
          accessCode      : String,
          description     : String,
          //reference to User ID
          members         : [Number],
          comments        :[Comment]
      });
  </code></pre>