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?

Relevant read - http://mongoosejs.com/docs/queries.html – Adam Zerner Jul 31 '15 at 16:58 — Adam Zerner, Jul 31 '15 at 16:58

score 48 · Answer 1 · edited Jul 05 '15 at 21:27

48

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

edited Jul 05 '15 at 21:27

Adam Zerner

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answered Jan 08 '14 at 03:46

Alexander Shtuchkin

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12

The newest version of mongoose also lets you use the result of `find()` as a promise, without needing to call `exec`. So you could just do: `Content.find({route: r}).then(function(content) { } );` – Jamie Jul 10 '15 at 18:38
why do you use res.local? can you directly use `var a = myLib.process(req.path)` – OMGPOP Jul 15 '15 at 07:40
@OMGPOP I think OP wanted to use promise in templates. Yes, you can use it directly. – Alexander Shtuchkin Jul 16 '15 at 08:24

score 30 · Answer 2 · answered May 09 '14 at 08:56

30

Mongoose already uses promises, when you call exec() on a query.

var promise = Content.find( {route : r }).exec();

answered May 09 '14 at 08:56

konsumer

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2

As of Mongoose 4.13, `find()` already returns a promise. No need to call `exec()`. – Mark Stosberg Dec 30 '17 at 19:22

Alexey B. · Answer 3 · 2015-10-29T08:43:06.627

23

Mongoose 4.0 Release Notes

Mongoose 4.0 brings some exciting new functionality: schema validation in the browser, query middleware, validation on update, and promises for async operations.

With mongoose@4.1 you can use any promises that you want

var mongoose = require('mongoose');
mongoose.Promise = require('bluebird');

Another example with polyfilling global.Promise

require('es6-promise').polyfill();
var mongoose = require('mongoose');

So, you can just do later

Content
  .find({route : r})
  .then(function(docs) {}, function(err) {});

Or

Content
  .find({route : r})
  .then(function(docs) {})
  .catch(function(err) {});

P.S. Mongoose 5.0

Mongoose 5.0 will use native promises by default if available, otherwise no promises. You will still be able to set a custom promises library using mongoose.Promise = require('bluebird');, however, mpromise will not be supported.

edited Oct 29 '15 at 08:43

answered Sep 16 '15 at 07:31

Alexey B.

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could you give an example of native promise use with mongoose 5.0 ? – Martin Nov 13 '15 at 17:19
Mongoose 5.0 not released yet – Alexey B. Nov 16 '15 at 08:30
i have imported like `import { Mongoose } from "mongoose";` in this case how can i use bluebird and promise? – Sunil Garg Apr 28 '21 at 12:10

score 5 · Answer 4 · edited Jun 13 '15 at 06:00

5

I believe you're looking for

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

  Content.find( {route : r }, function (err, docs) {
     if(err) {
       promise.error(err);
       return;
     }
     promise.complete(docs);

  });

  return promise;

};

edited Jun 13 '15 at 06:00

royhowie

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answered Jan 31 '12 at 14:32

deedubs

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score 0 · Answer 5 · answered Jan 12 '17 at 04:14

0

On this page:http://mongoosejs.com/docs/promises.html

The title is Plugging in your own Promises Library

answered Jan 12 '17 at 04:14

Mr.Thanks

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score -1 · Answer 6 · answered Aug 11 '15 at 18:58

-1

Use the bluebird Promise library like this:

var Promise = require('bluebird');
var mongoose = require('mongoose');
var mongoose = Promise.promisifyAll(mongoose);

User.findAsync({}).then(function(users){
  console.log(users)
})

This is thenable, such as:

User.findAsync({}).then(function(users){
      console.log(users)
    }).then(function(){
      // more async stuff
    })

answered Aug 11 '15 at 18:58

Anthony

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This answer is outdated. Mongoose already has native promise support support, so there is no need to Promisify the methods. – Mark Stosberg Dec 30 '17 at 19:21
This would be for versions prior to 4.0 – Anthony Dec 31 '17 at 02:43

How to use mongoose Promise - mongo

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