Example of reading aggregates in rom-rb

rom_reading_aggregates.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required.'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'rom'
  gem 'rom-sql'
  gem 'rom-repository'
  gem 'sqlite3'
  gem 'rspec'
  gem 'pry'
  gem 'pg'
end

require 'rspec/autorun'

describe ROM::Repository do
  let(:rom) { ROM.container(configuration) }
  let(:configuration) do
    ROM::Configuration.new(:sql, 'postgres://localhost:5432/rom_repository').tap do |config|
      config.gateways[:default].connection.drop_table?(:tags)
      config.gateways[:default].connection.drop_table?(:posts)

      config.default.create_table(:posts) do
        primary_key :id
        column :title, String, null: false
      end

      config.default.create_table(:tags) do
        primary_key :id
        foreign_key :post_id, :posts, null: false
        column :name, String, null: false
      end

      config.relation(:posts) do
        schema(infer: true) do
          associations do
            has_many :tags
          end
        end

        view :with_tags do
          schema do
            posts = relations[:posts].qualified
            tags = relations[:tags].qualified
            new([
                  posts[:id],
                  posts[:title],
                  *tags.project { array::array_agg(tags[:name]).as(:tag_names) }.schema
                ])
          end

          relation do
            join(tags).group(self[:id].qualified)
          end
        end
      end
    end
  end

  let(:repo) do
    Class.new(ROM::Repository[:posts]) do
      relations :tags
    end.new(rom)
  end

  let(:post_id) { repo.root.insert(title: 'post 1') }
  let(:posts) { repo.root.with_tags.to_a }

  before { repo.tags.insert(post_id: post_id, name: 'tag 1') }
  before { repo.tags.insert(post_id: post_id, name: 'tag 2') }

  it { expect(posts.count).to eq 1 }
  it { expect(posts.first.title).to eq 'post 1' }
  it { expect(posts.first.tag_names).to eq ['tag 1', 'tag 2'] }
end