dci2.rb

# Role base class. Use SimpleDelegator instead?
class Role
  def initialize(player)
    @player = player
  end
  # should be public send ?
  def method_missing(s, *a, &b)
    @player.__send__(s, *a, &b)
  end
end

# Context (UseCase) base class.
class Context
  def cast(player, role)
    role.new(player)
  end
end


# --- example ---

# Mixins are fixed roles.
module Balance
  def initialize
    @balance = 0
  end
  def availableBalance
    @balance
  end
  def increaseBalance(amount)
    @balance += amount
  end
  def decreaseBalance(amount)
    @balance -= amount
  end
end

#
class Balance::TransferSource < Role
  def transfer(amount)
    decreaseBalance(amount)
    puts "Tranfered from account #{__id__} $#{amount}"
  end
end

#
class Balance::TransferDestination < Role
  def transfer(amount)
    increaseBalance(amount)
    puts "Tranfered to account #{__id__} $#{amount}"
  end
end

# We can think of a context as setting a scene.
class Balance::Transfer < Context
  attr_reader :source_account, :destination_account
  def initialize(source_account, destination_account)
    @source_account      = cast(source_account, Balance::TransferSource)
    @destination_account = cast(destination_account, Balance::TransferDestination)
  end
  def transfer(amount)
    source_account.transfer(amount)
    destination_account.transfer(amount)
  end
end

class Account
  # An account by definition has a balance.
  include Balance
end

acct1 = Account.new
acct2 = Account.new

Balance::Transfer.new(acct1, acct2).transfer(50)