Node.js猫鼬回调

Question

I saw a lot of answers but im still unable to make this work. I have a simple function that i want to return a length of a query find on Mongoose. It goes like:

app.use(function(req, res, next) {
        res.locals.user = null
        if (req.isAuthenticated()) {
            res.locals.user = req.user;
            getMt(req.user.id, function(val) {
                console.log(val) // == 5
                res.locals.mt = val;
            });
        }
        console.log(res.locals.mt); // == undefined
....
}
function getMt(user_id, callback) {
    var Model = require('./models/mt');
    Model.find({'users.user_id': user_id}, 'token', function(err, list) {
        if (err)
            callback(0);
        if (!list)
            callback(0);
        if (list)
            callback(list.length);
    });
}

I read a lot about async, and i still cant find a solution for this. res.locals.mt still shows me undefined after the res.locals.mt = val inside the callback.

Can someone point me in the right direction? Thanks in advance.

Answer 1

Does this get you where you're trying to go?

function getMt(user_id, callback) {
    var Model = require('./models/mt');
    Model.count({'users.user_id': user_id}, function(err, count) {
        if (err) {
            console.log(err.stack);
            return callback(0);
        }
        callback(count);
    });
}

Answer 2

call next function!

app.use(function(req, res, next) {
        res.locals.user = null
        if (req.isAuthenticated()) {
            res.locals.user = req.user;
            getMt(req.user.id, function(val) {
                console.log(val) // == 5
                res.locals.mt = val;
                next(); //<---- add this!!!
            });
        }
....
}