CODEWITHSUNDEEP
sails.jswaterline
Alex Lenail
Alex Lenail

Reputation: 14440

sails many to many model association fails to save

I'm using recently released sails v0.10.2 and I can't get a many-to-many model association to work. Here's what I'm trying to build: 

// models/Group.js
module.exports = {

    identity: 'Group',

    attributes: {
    ...
        admins: {
            collection: 'User',
            via: 'groups',
            dominant: true
        },
    ...

// models/User.js
module.exports = {

    identity: 'User',

    attributes: {
    ...
        groups: {
            collection: 'Group',
            via: 'admins'
    },
    ...

This, to my knowledge, should set up a Many-to-Many association between these models. Both of them are stored on sails-memory for development. 

// function is called when a group-creation form is filled in the frontend.
create: function(req, res, cb) {

    Group.create( req.params.all() ).exec( function(err, group) {

        if (err) { console.log(err); return cb(err); }
        else { 
            group.admins.add(req.user.id);
            group.save(function(err){
                if(err){console.log(err);}
                else {
                    console.log('binding user to group:');
                    console.log(req.user);
                    console.log(group);
                }

            });

            res.json(group); 

        }

    });


},

The output looks like this: 

binding user to group
{ username: me
  .. some other things ..
  createdAt: Sat Aug 09 2014 10:13:15 GMT-0700 (PDT),
  updatedAt: Sat Aug 09 2014 10:13:24 GMT-0700 (PDT),
  id: 1 }
{ name: 'this is my group',
  description: 'this is mah desccription',
  tags: [ 'tag' ],
  createdAt: Sat Aug 09 2014 10:13:43 GMT-0700 (PDT),
  updatedAt: Sat Aug 09 2014 10:13:43 GMT-0700 (PDT),
  id: 1 }

Which to me means that the groups field of the user model is not being modified, because not only isn't it present, but the updatedAt field doesn't register a change. There exist a couple possible reasons this is failing that I can think of:

Upvotes: 1

Views: 839

Answers (1)

Alex Lenail
Alex Lenail

Reputation: 14440

So it turns out that I understand nothing about databases and joins. My assumption was essentially this:

My model has an admins attribute and the Groups.admins.add() function will find the User model and just kind of put a link to a user model in there, such that res.json(group) will return the group with an admins attribute populated with a User object on its own.

That turns out to not be the case, you need to manually .find() then .populate('fieldName') the model, which probably saves a bunch of overhead on the database end.

I initially had ~10 suspects (4 of which are sill above) and while knocking them out, I opened an issue frivolously on the sails-memory github, which a friendly banana helped me resolve.

https://github.com/balderdashy/sails-memory/issues/13#issuecomment-51862742

Upvotes: 1

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