exports.getByUserId = (req, res) => {
  User.findById(req.params.userId).then(user => {
    if(!user) {
      return res.status(404).send({
        message: "User not found with id " + req.params.userId
      });
    }

    Studentclass.findById(user.class).then(studentClass => {
      if(!studentClass) {
        return res.status(404).send({
          message: "Class not found with id " + user.class
        });
      }

    Course.find()
    .populate({
      path: 'room',
      model: 'Room',
      populate: {
        path: 'beacon',
        model: 'Beacon'
      }
    }).then(courses => {
      if(!courses) {
        return res.status(404).send({
          message: "No course was found"
        });
      }

      var filteredCourses = courses.filter(function(course) {
        if (course.class != null) {
          return course.class.equals(studentClass._id)
        } else {
          return false
        }
      })

      return res.status(200).send(filteredCourses);
    }).catch(err => {
        res.status(500).send({
            message: err.message || "Error on Course."
        })});
  }).catch(err => {
      res.status(500).send({
          message: err.message || "Error on Class."
      })});
}).catch(err => {
    res.status(500).send({
        message: err.message || "Error on User."
    })})}