javascript - How to inserting a document with field referencing document in another collection -

i attempting create .post function schema document reference. however, not sure how can retrieve objectid of document reference collection.

board.js

var mongoose     = require('mongoose'); var schema       = mongoose.schema;  var boardschema   = new schema({ boardname: string, userid: {type: schema.objectid, ref: 'userschema'} });  module.exports = mongoose.model('board', boardschema); 

user.js

var mongoose     = require('mongoose'); var schema       = mongoose.schema;  var userschema   = new schema({     username: string });  module.exports = mongoose.model('user', userschema); 

routes.js

router.route('/boards')  .get(function(req, res) {     board.find(function(err, boards) {         if(err)             res.send(err);          res.json(boards);     }); })  .post(function(req, res) {      var board = new board();     board.boardname = req.body.boardname;      user.find({username: req.body.username}, function(err, user) {         if(err)             res.send(err);          board.userid = user._id;     });      board.save(function(err) {         if(err)             res.send(err);          res.json({message: 'new board created'});     }); }); 

to create board, include boardname , username in request. using username, user.find find specific user , assign board.userid. however, not seem working board.userid not appear.

any appreciated!

thank you!

edit

a better explanation of required have existing user collection. when want add new document board, provide username, search user collection, obtain objectid of specific user , add userid board document.

believe looking population

there no joins in mongodb still want references documents in other collections. population comes in.

try this:

//small change board schema var boardschema   = new schema({    boardname: string,    user: {type: schema.objectid, ref: 'user'} });   //using populate board.findone({ boardname: "someboardname" })    .populate('user') // <--    .exec(function (err, board) {       if (err) ..       console.log('the user %s', board.user._id);       // prints "the user id <some id>"    }) 

sorry, solved different problem previously. you'll want use prevoius solution provided @ point, i'm leaving it.

callbacks

the reason userid not on board document because user.find asynchronous , not assigned @ moment board.save(...) called.

this should trick:

(also, added couple of returns prevent execution after res.send(...))

.post(function(req, res) {      var board = new board();     board.boardname = req.body.boardname;      user.find({username: req.body.username}, function(err, user) {         if(err)             return res.send(err); //<-- note return here!          board.userid = user._id;          board.save(function(err) {            if(err)             return res.send(err); //<-- note return here!             res.json({message: 'new board created'});         });     });    });