Decorators in Ruby (migrating from Python)

Here’s another approach that eliminates the problem with conflicts between names of aliased methods (NOTE my other solution using modules for decoration is a good alternative too as it also avoids conflicts):

module Documenter
    def document(func_name)   
        old_method = instance_method(func_name) 

        define_method(func_name) do |*args|   
            puts "about to call #{func_name}(#{args.join(', ')})"  
            old_method.bind(self).call(*args)  
        end
    end
end

The above code works because the old_method local variable is kept alive in the new ‘hello’ method by fact of define_method block being a closure.