node.js - How to use mongoose Promise - mongo

Question

Can someone give me an example on how to use a Promise with mongoose. Here is what I have, but its not working as expected:

app.use(function (req, res, next) {
  res.local('myStuff', myLib.process(req.path, something));
  console.log(res.local('myStuff'));
  next();
});

and then in myLib, I would have something like this:

exports.process = function ( r, callback ) {
  var promise = new mongoose.Promise;
  if(callback) promise.addBack(callback);

  Content.find( {route : r }, function (err, docs) {
     promise.resolve.bind(promise)(err, docs);

  });

  return promise;

};

At some point I am expecting my data to be present, but how can I access it, or get at it?

Answer 1

In the current version of Mongoose, the exec() method returns a Promise, so you can do the following:

exports.process = function(r) {
    return Content.find({route: r}).exec();
}

Then, when you would like to get the data, you should make it async:

app.use(function(req, res, next) {
     res.local('myStuff', myLib.process(req.path));
     res.local('myStuff')
         .then(function(doc) {  // <- this is the Promise interface.
             console.log(doc);
             next();
         }, function(err) {
             // handle error here.
         });
});

For more information about promises, there's a wonderful article that I recently read: http://spion.github.io/posts/why-i-am-switching-to-promises.html