config_dsl.rb

# Encapsulate the configuration DSL pattern.
# 
# Any `X=(value)` setter method on the given +obj+ is translated into `X(value)` method
# in the context of this object.
class ConfigDSL < BasicObject
  def initialize(obj, &config)
    @self = obj
    call(&config)
  end

  # Calls the &config block in the context of self.
  #
  # If the arity of the block is == 1 then self is passed to the block rather
  # than changing execution context to self.
  def call(&config)
    if config.arity == 1
      config.call(self)
    else
      instance_exec(&config)
    end
  end

  # Forwards all naked methods as setter methods.
  #
  # Example:
  #    method_missing("foo", 3) tries to call @self.foo=(3)
  def method_missing(method, *args, &b)
    setter = "#{method.chomp ?=}="
    if args.size == 1 && @self.respond_to? setter
      @self.__send__(setter, *args, &b)
    else
      @self.__send__(method, *args, &b)
    end
  end

  # Because meta
  def to_proc
    method(:call)
  end
end

if __FILE == $0

class Foo
  attr_accessor :a, :b, :c
end

foo = Foo.new

ConfigDSL.new(foo) do
  a "333"
  b 2452253425
  c a
end

p foo

end