CODEWITHSUNDEEP
expressmongoose
Soo
Soo

Reputation: 397

mongoose save by reference multiple document

I'd like to make new document by reference of two documents. 

**app.post('/student_badge/register', async (req, res) => {
const name = req.body.name;
const category = req.body.category;

People.find({name: name}, '_id', function (err, doc) {
    if (err) return handleError(err);
    var obj = eval(doc);
    id = obj[0]._id;
  })

  Badge.find({category: category}, 'points title', function (err, doc)  {
      if (err) return handleError(err);
      var obj2 = eval(doc);
      points = obj2[0].points;
      title = obj2[0].title;
      console.log(title + "  " + points);
  });


  data = {
    id: id,
    title: title,
    points: points
  }


  console.log("data: " + data);   
  const sbadge = new StudentBadge(data);

  sbadge.
  save()
  .then(result => {
    res.status(201).json({
      message: 'Post created successfully!',
      post: result
    });
  })
  .catch(err => {
    console.log(err);
  });
});**

But I cannot call three variables like id, title, points to store them in 'data'. How can I call variables?

Thanks

Upvotes: 0

Views: 35

Answers (1)

gasbi
gasbi

Reputation: 848

Your code does not work because the variables you are trying to access, i.e. id, title, points, are being set on a callback function that gets executed asynchronously.

I would suggest using async/await instead of callbacks so that you can thereafter use the data from the other documents you are querying in the same function. In addition, I suggest to use findOne() since you only access the first entry in db.

Something like the example below should work: (I have abstracted the middleware in a separate function for clarity to use with express) 

const createStudentBadge = async (req, res, next) => {
  const {name, category} = req.body;

  let person, badge;
  try {  
    person = await Person.findOne({name}); // shortcut for {name: name}
    badge = await Badge.findOne({category});
  } catch(err) {
    // handle error
  }

  if (!person || !badge) {
    // Handle case where no document has been found in db
    // This case will not throw an error when calling find()
  }

  data = {
    id: person._id,
    title: badge.title,
    points: badge.points
  }

  const studentBadge = new StudentBadge(data);

  try {
    await studentBadge.save();
  } catch(err) {
    // handle error
  }

  res.status(201).json({
    message: 'Post created successfully!',
    post: studentBadge
  });
}

app.post('/student_badge/register', createStudentBadge);

If you wanted to perform the querying in parallel, you could make use of Promise.all() and run both queries at the same time. More info can be found at MDN documentation

Upvotes: 1

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