Keystone JS - Update / seeding / with Relationship

Question

I'm fairly new to KeystoneJS and struggle with pre-populating a database through seeds / updates. I have no problem with independent properties but struggle with properties with relationships.

I have for example a Location Model that includes photos.

var Location = new keystone.List('Location', {
  sortable: true,
  autokey: {
    path: 'slug',
    from: 'name',
    unique: true
  }
});    

Location.add({
  name: {
    type: Types.Text,
    required: true,
    initial: true
  },
  photos: {
    type: Types.Relationship,
    ref: 'Photo',
    many: true
  }
}

and the Photo Model is as such:

var Photo = new keystone.List('Photo', {
    autokey: {
        path: 'slug',
        from: 'title',
        unique: true
    }
});    

Photo.add({
    title: {
        type: Types.Text,
        initial: true,
        index: true
    },
    image: {
        type: Types.CloudinaryImage,
        required: true,
        initial: false
    }
});    

Photo.relationship({
    ref: 'Location',
    path: 'photos',
    refPath: 'photos'
});

Within the update folder I'm trying to seed the database with pre-loaded data. Both Location and Photo models get populated individually but I am failing to pre-populate the relationship within both within the Admin UI and lacks knowledge on how to solve. I did quite some research, tried different things such as using __ref and _ids but couldn't make it work. I could not find the answer within the KeystoneJS documentation either. Maybe there is something obvious that I'm actually missing.

exports.create = {
    Location: [
        {
            name: 'London',
            photos: [
                // <-- how to do it here? 
            ]
        },
        {
            name: 'New York',
            photos: [
                // <-- how to do it here? 
            ]
        }
    ]
};

Would anyone know the right way to pre-populate KeystoneJs database relationships? Thank you very much.

Answer 1

I managed to solve by mapping through the photos and replace by the actual photo found by title. Here is how I did in case it can help someone else:

exports = module.exports = function (next) {
   Promise.all([
        {
            name: 'London',
            photos: ['london_1', 'london_2']
        },
        {
            name: 'New York',
            photos: ['new_york_1', 'new_york_2']
       }
    ].map(function (location) {
        var _photos = location.photos || [];
        location.photos = [];

        return Promise.all([
            _photos.map(function (title) {
                return Photo.model.findOne({ title: title })
                .then(function (photo) {
                     location.photos.push(photo);
                });
            })
        ])
        .then(function () {
            new Location.model(location).save();
        });
    }))
    .then(function () {
        next();
    })
    .catch(next);
};