Meteor. Sorting my collection by a deeply nested value

Question

In my application I have a list of tiles representing each project in a portfolio. This is the main list view for the app and all projects are fetched from the collection without any sorting or ordering.

When I have an optional slug parameter specified in my route (for the category assigned to the project) I want to be able to display the projects within the UI that match that category first, and then display the other ones that don't match the category.

For reference, I have included the code for the route below:

/** 
 *  Project list view (all projects) with optional 
 *  filter parameter for showing projects only by 
 *  their category name.
 */ 
this.route('list', {
    path: '/:_category_slug?',
    template: 'template_main',
    action: function() {
        if(this.ready()) {
            this.render();
        }
    },
    waitOn: function() {
        return [
            Meteor.subscribe('projects'), 
            Meteor.subscribe('formations'),
            Meteor.subscribe('categories')
        ];
    },
    data: function() {

        if(this.params._category_slug) {
            /**
             * Building up the query given the category slug and the language
             */
            var query = {};
            query['slug.' + App.language] = this.params._category_slug;

            /**
             *  Grab the category given the query, so we can get its 'id'
             */
            var category = App.models.categories.findOne(query);

            /**
             *  This is the query I need to work on so that I can achieve what I want
             */
            return App.models.projects.find({}).fetch();

        }
        else {
            return App.models.projects.find({}).fetch();
        }
    },
    yieldTemplates: {
        'components_header': {to: 'header'},
        'views_list': {to: 'content'},
        'components_footer': {to: 'footer'}
    }
});

For reference, I have also included a sample of the data for three projects that is relevant to this question.

{
    "id": 10,
    "slug": {
        "en": "sample-english-slug",
    },
    "title": {
        "en": "Sample English Title",
    },
    "description": {
        "en": "A good description.",
    },
    "category_ids": [
        {
            "id": 5
        },
        {
            "id": 6
        }
    ],
},
{
    "id": 12,
    "slug": {
        "en": "another-sample-slug",
    },
    "title": {
        "en": "Another sample title",
    },
    "description": {
        "en": "Sample description three",
    },
    "category_ids": [
        {
            "id": 1
        },
        {
            "id": 4
        }
    ],
},
{
    "id": 11,
    "slug": {
        "en": "another-sample-slug",
    },
    "title": {
        "en": "A sample title",
    },
    "description": {
        "en": "Sample description",
    },
    "category_ids": [
        {
            "id": 2
        },
        {
            "id": 5
        }
    ],
}

So what I would want to do is make sure that given a category with an ID of 5, I want those first two projects to be the first two that appear.

Can this be done in meteor, without having to resort to writing extra logic in JS? One approach I did have once was to update each project from within the Client side collection (something I no longer do) and set a few extra attributes, then sort after that.

When dealing with syncing client and server collections, this is not really feasible.

Answer 1

From the mongodb docs:

Use the dot notation to match by specific fields in an embedded document. Equality matches for specific fields in an embedded document will select documents in the collection where the embedded document contains the specified fields with the specified values. The embedded document can contain additional fields.

I don't know if you can do it with a single query, but you can concat two complementary queries that use dot notation.

var selected = App.models.projects.find({'category_ids.id': category._id}).fetch();
var other = App.models.projects.find({'category_ids.id': {$ne: category._id}}).fetch();
return selected.concat(other);