$populate does not seem to work

[garrypolley]

Steps to reproduce

Create a linked relationship between two models

Expected behavior

When I query a basic endpoint I expect the $populate parameter to include my related model.

Actual behavior

The related model is not included in my results. The include never gets sent to sequelize and therefore the inner join is never made.

[daffl]

Does Sequelize support $populate? I thought that was a Mongoose thing.

[garrypolley]

They support an include which does about the same thing. So if I have hasMany relationship, I can add a:

.findAll({ include: 'MyManyModel' })

And it'll add the nested model via an inner join. I was assuming that a $populate would drop the value into include.

[garrypolley]

For further clarification --> http://docs.sequelizejs.com/en/latest/docs/models-usage/?highlight=include#including-everything

I think it'd be possible to do something like what's below, with maybe a bit more logic to use the proper model name/instance in the include.

return this.Model.findAndCount(q).then(result => {
      return {
        include: filters.$populate, // more logic may be needed to refer to the model by name. 
        total: result.count,
        limit: filters.$limit,
        skip: filters.$skip || 0,
        data: result.rows
      };
    }).catch(utils.errorHandler);

[daffl]

Yes, you can do that by setting params.sequelize in a hook:

app.service('sequelizeService').before({
  find(hook) {
    hook.params.sequelize = {
      include: hook.params.query.$populate
    }
  }
});

[garrypolley]

Thanks! That works with me doing a hooks.app.get('models')[hooks.params.query.$populate]

It'd be nice if it "just worked" out of the box though and not requiring a hook.

I suppose I could add a "global" hook, but those tend to look a little weird/hacky in implementation if I recall.

[daffl]

Not anymore, you can use app.hooks.

[garrypolley]

Awesome! That's exactly what I'd be happy with for now. Thanks for the help!

[L3V147H4N]

This does not work for me...

this.UsersService.find({
      query: {
        $sort: {
          name: 1
        },
        $populate: [
          {
            model: 'Role', as: 'roles'
          }
        ]
      }
    })
`

throws self.$expandAttributes is not a function

[sarkistlt]

@L3V147H4N it won't work because 'Role' is string not a model, I'm using this hook:

function resolveModels(arr, models) {
  const include = [];

  arr.forEach((entity) => {
    if (typeof entity === 'string') {
      include.push(entity);
    } else if (typeof entity === 'object') {
      if (entity.model && typeof models[entity.model] === 'function') {
        entity.model = models[entity.model];
      }
      if (entity.include && Array.isArray(entity.include)) {
        entity.include = resolveModels(entity.include, models);
      }
      include.push(entity);
    }
  });

  return include;
}

export default function sequalizePopulateHook(ctx) {
  if (
    ctx.params.query &&
    ctx.params.query.$populate &&
    Array.isArray(ctx.params.query.$populate)
  ) {
    const { models } = ctx.app.get('sequelize');

    ctx.params.sequelize = ctx.params.sequelize || {};
    ctx.params.sequelize.include = resolveModels(ctx.params.query.$populate, models);
    ctx.params.sequelize.raw = false;

    delete ctx.params.query.$populate;
  }
  return ctx;
}

it will resolve model from string in:

$populate: [
  {
    model: 'Role', as: 'roles'
  }
]