Immutable after construction pattern

gistfile1.ru

class ConstructorHelper
  class << self
    def construct(target, writers_for = target.instance_variables, &block)
      self.new(target, writers_for).instance_eval(&block) if block_given?
    end
  end

  def initialize(target, writers_for = target.instance_variables)
    writers_for.each do |variable|
      self.class.send(:define_method, :"#{ variable.to_s.sub(/^:?@/, '') }=") do |v|
        target.instance_variable_set(variable, v)
      end
    end
  end
end

gistfile2.ru

class ImmutableAfterConstruction
  attr_reader :variable1
  attr_reader :variable2

  def initialize(&block)
    @variable1, @variable2 = 'foo', 'bar'
    ConstructorHelper.construct(self)
  end
end

value = ImmutableAfterConstruction.new do
  self.variable1 = 'Hello'
  self.variable2 = 'World!'
end
puts value.inspect