class_macro.rb

class Book
  def title(title)
    puts title
  end

  def self.deprecate(old_method, new_method)
    define_method(old_method) do |*args, &block|
    warn "Warning: #{old_method}() is deprecated. Use #{new_method}()."
    send(new_method, *args, &block)
    end
  end

  deprecate :GetTitle, :title
end

b = Book.new
b.GetTitle("foo")
b.title("bar")