Installation

Install the gem and add to the application's Gemfile by executing:

$ bundle add active_dry_deps

Dependency Injection

Dependency injection helps to break explicit dependencies between objects making it much easier to maintain a single responsibility and reduce coupling in our class designs. This leads to more testable code and code that is more resilient to change.

For a deeper background on Dependency Injection consider the Wikipedia article on the subject.

Usage

Basic

Under the hood active_dry_deps uses a container like dry-container and convert key to underscore for fetch from container. For auto-registration dependencies use dry-system.

MyApp::Container.register('warehouse.create_departure_service', Class.new { def self.call = 'failure' })
include Deps['Warehouse::CreateDepartureService.call']

Deps['Warehouse::CreateDepartureService.call'] this notation is familiar to Ruby developers, helps to find code in the project, and simplifies the migration from constants in code to defining dependencies.

class CreateOrderService < ServiceObject

  include Deps[
    'Warehouse::CreateDepartureService.call',
    'Warehouse::ReserveJob.perform_later',
    'OrderMailer',
    'redis',
    track: 'StatsApi.message',
  ]

  def call(params)
    order = Order.create(params)

    ReserveJob(order)
    track(order.id, order.created_at)

    redis.with do |conn|
      conn.incr('order_count')
    end

    OrderMailer().with(user: user).deliver_later

    CreateDepartureService(order.slice(:id, :departure_at))
  end

end

describe 'CreateOrderService' do
  it 'success create order' do
    service = described_class.new(user: create(:user), zip_code: 67_345)
    expect(service).to deps(CreateDepartureService: double(success?: true), ReserveJob: spy, track: spy)

    expect(service.call.success?).to be true
  end
end

Import methods

You can inject any method from object in your container

MyApp::Container.register(:str, 'str')
MyApp::Container.register(:service, Module.new { def self.success? = true } )

include Deps['str.reverse', 'service.success?']
reverse # => "rts"
success? # => true

Import callable methods

By default, when call or perform_later methods are imported, the name of the dependency is taken from the name of the constant:

  include Deps[
    'Warehouse::CreateDepartureService.call', # callable
    'Warehouse::ReserveJob.perform_later', # callable
    'Warehouse::ReserveJob.perform_now',
    'Warehouse::ProductActivateQuery',
  ]

  # use as
  CreateDepartureService()
  ReserveJob()
  perform_now
  ProductActivateQuery().run

Recommends using prefixes (Service, Job, Query) in the name of the constant for easy reading of the dependency type.

Aliases

include Deps[string: 'str.reverse', m: 'module']
string # => "rts"
m # => "success"

Tests (Rspec)

deps

gem adds rspec matcher for stub dependency, put require 'active_dry_deps/rspec' to rspec setup

GpApp::Container.register('order.dependency', Class.new { def self.call = 'failure' })

let(:service_klass) do
  Class.new do
    include Deps['Order::Dependency.call']

    def call = Dependency()
  end
end

it 'failure' do
  expect(service_klass.new.call).to be 'failure'
end

it 'success' do
  service = service_klass.new
  expect(service).to deps(Dependency: 'success')

  expect(service.call).to be 'success'
end

stub, unstub

it 'stub' do
  Deps.stub('Order::Dependency', double(call: 'success'))
  expect(service_klass.new.call).to be 'success'

  Deps.unstub('Order::Dependency') # or simple Deps.unstub for unsub all keys
  expect(service_klass.new.call).to be 'failure'
end

Configuration

gem auto-configuring, but you can override settings

ActiveDryDeps.config.container = 'MyApp::Container'
ActiveDryDeps.config.inflector = ActiveSupport::Inflector
ActiveDryDeps.config.inject_global_constant = 'Deps'

Recommended container setup with dry-system for Rails

config/initializers/system.rb

require 'dry/system/container'

module GpApp
  class ContainerRailtie < Rails::Railtie

    LOADER =
      Class.new(Dry::System::Loader) do
        def self.call(component, *args)
          constant = self.constant(component)

          if singleton?(constant)
            constant.instance(*args)
          else
            constant # constant.new(*args) - THIS LINE REWRITED from Dry::System::Loader
          end
        end
      end

    # https://api.rubyonrails.org/classes/Rails/Railtie.html
    # Add a to_prepare block which is executed once in production
    # and before each request in development.
    config.to_prepare do
      ContainerRailtie.finalize
    end

    def finalize
      set_or_reload(:Container, create_container)
      Dry::System.register_provider_sources(Pathname(__dir__).join('../system/providers').realpath)
      create_container.finalize!(freeze: !(::Rails.env.test? || ::Rails.env.development?))
    end

    def create_container
      Class.new(Dry::System::Container) do
        configure do |config|
          config.inflector = ActiveSupport::Inflector
          config.root = Rails.root.join('app')

          %w[domains jobs queries services mailers].each do |dir_name|
            config.component_dirs.add dir_name do |dir|
              dir.loader = LOADER
              dir.memoize = true
            end
          end

          config.component_dirs.add '../lib' do |dir|
            dir.loader = LOADER
            dir.memoize = true
          end
        end
      end
    end

    def set_or_reload(const_name, const)
      remove_constant(const_name)
      GpApp.const_set(const_name, const)
    end

    def remove_constant(const_name)
      if GpApp.const_defined?(const_name, false)
        GpApp.__send__(:remove_const, const_name)
      end
    end

  end
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/corp-gp/active_dry_deps.

License

The gem is available as open source under the terms of the MIT License.