Question

Below is code for a class that can dynamically add logging to a method. This works in the case where the method takes no parameters and accepts no block.

How can I rewrite the code, so that I can add logging of a method even if it accepts parameters and accepts a block?

class X
    def greet
        puts "hi"
    end

    def self.add_logging(method_name)
        alias_method("original_#{method_name}".to_sym, method_name) 

        #How do i rewrie this to account for method_name's arguments and ability to accept a block?
        define_method(method_name) do
            puts "calling #{method_name}"
            send "original_#{method_name}".to_sym
            puts "done #{method_name}"
        end
    end
end

x = X.new
x.greet
X.add_logging(:greet)
x.greet

outputs

>hi 
>calling greet 
>hi 
>done greet

Answer 1

class X
  def self.add_logging method
    alias_method "original_#{method}", method
    define_method(method) do |*args, &pr|
      puts "calling #{method}"
      send "original_#{method}", *args, &pr
      puts "done #{method}"
    end
  end
  def greet person
    puts "hi #{person}"
  end
end

x = X.new
x.greet("Joe")
X.add_logging(:greet)
x.greet("Jane")

will give:

hi Joe
calling greet
hi Jane
done greet