Set session value in callback (Node.js, express.js)

Question

How to set session value in callback? Why it doesn't work?

app.get('/room/:id', function(req, res) {
    var room_id = req.param('id');
    room.getRoom(room_id, function(err, result) {
        if(result.length) {
            req.session.code_room = room_id;
        }
    }); 
    res.render('room.jade');
});

Answer 1

You probably should move res.render to the inside of callback function:

app.get('/room/:id', function(req, res) {
    var room_id = req.param('id');
    room.getRoom(room_id, function(err, result) {
        if(result.length && !err) {
            req.session.code_room = room_id;
        } else {
            //sorry...
            req.session.code_room = -1;
        }
        res.render('room.jade');
    }); 
});