rom_view_example.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'
end

require 'rspec/autorun'

describe ROM::Repository do
  let(:rom) { ROM.container(configuration) }
  let(:configuration) do
    ROM::Configuration.new(:sql, 'sqlite::memory').tap do |config|
      config.default.create_table(:users) do
        primary_key :id
        column :name, String, null: false
      end

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

      config.relation(:users) do
        schema(infer: true)

        view(:for_posts, schema) do |posts|
          where(id: posts.pluck(:user_id))
        end
      end
    end
  end

  let(:repo) do
    Class.new(ROM::Repository[:posts]) do
      relations :users

      def all
        posts.combine(one: {user: [users.for_posts, user_id: :id]})
      end
    end.new(rom)
  end

  before { create_post(title: 'post_title', user_name: 'Sergiy') }

  it 'contains 1 user' do
    expect(repo.users.count).to eq 1
  end

  it 'contains 1 post' do
    expect(repo.posts.count).to eq 1
  end

  let(:first) { repo.all.limit(1).one }

  it 'combines posts with users' do
    expect(first.user.name).to eq 'Sergiy'
  end

  def create_post(attrs)
    user_id = rom.relations[:users].insert(name: attrs.fetch(:user_name))
    rom.relations[:posts].insert(title: attrs.fetch(:title), user_id: user_id)
  end
end

Failures:

  1) ROM::Repository combines posts with users
     Failure/Error: expect(first.user.name).to eq 'Sergiy'

     NoMethodError:
       undefined method `name' for #<ROM::Struct[User]>
     # rom_value_object_save.rb:68:in `block (2 levels) in <main>'

Finished in 0.0636 seconds (files took 0.19648 seconds to load)
3 examples, 1 failure

first.to_h returns {:id=>1, :user_id=>1, :title=>"post_title", :user=>{}}