http://twitter.com/svenfuchs/status/34904397171400704

class_with_attr_reader.rb

class Class
  def self.with_reader(name, &block)
    Class.new do
      attr_reader :"#{name}"
      define_method :initialize do |value|
        instance_variable_set("@#{name}", value)
      end
      class_eval(&block) if block_given?
    end
  end
end

Foo = Class.with_reader(:bar) do
  def moo; "moo"; end
end

foo = Foo.new(123)
puts foo.bar
puts foo.moo