intro.md

Ruby Cake

A quick experiment trying to replicate the cake pattern example from Jonas Bonér's post Real-World Scala: Dependency Injection (DI) in ruby.

cake.rb

# From Jonas Bonér's post on The Cake Pattern

module UserRepositoryComponent
    class UserRepository
	def authenticate(user) 
	    puts "Authenticating user: #{user}"
	    user
	end

	def create(user)
	    puts "Creating user: #{user}"
	end

	def delete(user)
	    puts "Deleting user: #{user}"
	end
    end
end

module UserServiceComponent # this: UserRepositoryComponent
    def self.included (klass)
	userServiceWithRepository = Class.new(UserServiceComponent::UserService) do
	    # using def here will cause us to lose a reference to the closed-over 
	    # environment, and hence klass.
	    define_method :userRepository do
		klass.userRepository
	    end
	end
	klass.const_set(:UserService, userServiceWithRepository)
    end
    class UserService
	User = Struct.new(:username, :password)

	def authenticate(username, password)
	    userRepository.authenticate(username, password)
	end

	def create(username, password)
	    userRepository.create(User.new(username, password))
	end

	def delete(user)
	    userRepository.delete(user)
	end
    end
end

module ComponentRegistry
    include UserServiceComponent
    def self.userService
	@userService ||= UserService.new
    end

    include UserRepositoryComponent
    def self.userRepository
	@userRepository ||= UserRepository.new
    end
end

if $0 == __FILE__
    ComponentRegistry.userService.create('fred', 'moo')
end