node.js - moongose subschema not working -

var commentschema = new schema({  rating:  {     type: number,     min: 1,     max: 5,     required: true  },  comment:  {     type: string,     required: true  },  postedby: {     type: mongoose.schema.types.objectid,     ref: 'user',     index:true  }  },{    timestamps: true  });   var postschema = new schema({   title:{     type:string,     required:true    },   image:{    type:string,    required:true   },   meta:{    type:string,    required:true   },   story:{    type:string,    required:true   },  likes:{    type:number,    min:0,    required:true   },   postedby: {     type: mongoose.schema.types.objectid,     ref: 'user',     index:true    },  comments:[commentschema] }, {  timestamps: true  }); 

this schema design

.get(function(req,res,next){   posts.find({})   .populate('postedby')   .populate('comments.postedby')   .exec(function (err, post) {     if (err) throw err;     res.json(post); }); 

user schema

var user = new schema({ username: string, password: string, firstname: {   type: string,     default: '' }, lastname: {   type: string,     default: '' }, biodata: {   type: string,   default: '' }, admin:{     type: boolean,     default: false } }); 

but mongoose schema not working yet output shows nothing postedby field not working

{ "_id": "57d76b26a404a9072c43db0e", "updatedat": "2016-09-13t03:13:10.901z", "createdat": "2016-09-13t02:57:42.894z", "title": "long time no shot!", "image": "https://d13yacurqjgara.cloudfront.net/users/501822/screenshots/2946804/hot-shot.png", "meta": "this time, i'm exploring ui promo app. still exploration, feedback welcome :)", "story": "our last shot got lot of love , questions regarding project never going show , encouragement felt cool show entire spectrum of 2016 annual report wrapped leading way ministry.the report full 28 page spread has specific type , color system unique system textures , brushes. first time have set restriction on type of texturing goes on specific elements within design, 1 of size. bit of game changer , exploring more of in future.to look: once had each spread completed laid out of final jpg images on large canvas. once had spreads arranged how wanted used our new granite photoshop action set faded / dramatic black , white feel cover of images. applied subtle texture , noise on top of isolated of vector badges , type elements, enlarged them, gave each loud orange color , set them lighten.thank kind words , encouragement!", "likes": 300, "__v": 3, "comments": [   {     "updatedat": "2016-09-13t03:04:27.408z",     "createdat": "2016-09-13t03:04:27.408z",     "rating": 4,     "comment": "test comment",     "_id": "57d76cbb54ce630ad8e3922f"   },   {     "updatedat": "2016-09-13t03:06:10.891z",     "createdat": "2016-09-13t03:06:10.891z",     "rating": 2,     "comment": "test comment",     "_id": "57d76d22d9be810530c26c25"   },   {     "updatedat": "2016-09-13t03:13:10.900z",     "createdat": "2016-09-13t03:13:10.900z",     "rating": 2,     "comment": "test comment",     "_id": "57d76ec6c4eba41e742e1bbf"   } ] } 

can tell me problem going on server shows no error.