title: Populating in array of object ids
body: <p>My schema:-</p>
  
  <pre><code>var playlistSchema = new Schema({
  name        : {type:String,require:true},
  videos      : {type:[mongoose.Schema.Types.ObjectId],ref: 'Video'},
  },{collection:'playlist'})
  
  var Playlist = mongoose.model('Playlist',playlistSchema);
  </code></pre>
  
  <p>I have some data in the database as exapmple:-</p>
  
  <pre><code>{
  "_id" : ObjectId("58d373ce66fe2d0898e724fc"),
  "name" : "playlist1",
  "videos" : [ 
      ObjectId("58d2189762a1b8117401e3e2"), 
      ObjectId("58d217e491089a1164a2441f"), 
      ObjectId("58d2191062a1b8117401e3e4"), 
      ObjectId("58d217e491089a1164a24421")
  ],
  "__v" : 0
  </code></pre>
  
  <p>}</p>
  
  <p>And the schema of Video is :-</p>
  
  <pre><code>var videoSchema = new Schema({
  name        : {type:String,required:true},
  createdAt   : {type:String,default:new Date()},
  isDisabled  : {type:Boolean,default:false},
  album       : {type: mongoose.Schema.Types.ObjectId, ref: 'Album'}
  },{collection:'video'})
  
  var Video = mongoose.model('Video',videoSchema);
  </code></pre>
  
  <p>Now in order to get the name of the all the videos in playlist i am trying the code:-</p>
  
  <pre><code> var playlistModel = mongoose.model('Playlist');
  let searchParam = {};
  searchParam._id = req.params.pid;
  playlistModel.findOne(searchParam)
  .populate('[videos]')
  .exec(function(err,found){
      if(err)
          throw err;
      else{
          console.log(found.videos[0].name);
      }
  })
  </code></pre>
  
  <p>But here i am getting the undefined result.I am not getting where i am wrong plzz anyone help me to short out this problem.</p>