lazy proxy

gistfile1.rb

class VirtualAccountProxy

  def initialize(&block)
    @block = block
  end

  def deposit(amount)
    return subject.deposit(amount)
  end

  def subject
    @subject || (@subject = @block.call)
  end

end

class BankAccount

  def initialize
    puts "initialize BankAccount"
  end
  
  def deposit(amount)
    puts "deposit #{amount}"
  end

end

proxy = VirtualAccountProxy.new{ BankAccount.new }
puts "initialize Proxy"
proxy.deposit(100)