antonym_accessor

antonym_accessor.rb

class Module
  def antonym_accessor(*args)
    if 2 == args.length
      from, to = args
      define_method("#{to}?") { not send "#{from}?" }
      define_method("#{to}=") {|val| send "#{from}=", ! val }
    elsif 1 == args.length && args.first.is_a?(Hash)
      args.first.each {|from, to| antonym_accessor from, to}
    else
      raise <<-EXCEPTION
        antonym_accessor expects either
          "antonym_accessor :from, :to"
        or "antonym_accessor :from => :to"
      EXCEPTION
    end
  end
end

class ExampleClass
  def private?() @private end
  def private=(p) @private = p end
  antonym_accessor :private => :public
  # or, if you prefer:
  # antonym_accessor :private, :public
end

e = ExampleClass.new
e.private = false
e.public? #=> true
e.public = true
e.private? #=> false