Tracing ruby method calls

tracer.rb

module Tracer
  def trace(method)
    method, ending = split_method_name(method)
    define_method "#{method}_with_trace#{ending}" do |*arguments|
      puts "called #{self.class}##{method}#{ending}(#{arguments.map(&:inspect).join(', ')})"
       returning(send("#{method}_without_trace#{ending}", *arguments)) do |v|
         if block_given?
           yield self, v
         end
         puts "#{self.class}##{method}#{ending} => #{v.inspect}"
       end
     end
     alias_method_chain "#{method}#{ending}", :trace
   end
   private
   def split_method_name(method)
     if ['?', '!'].include?(method.to_s[-1..-1])
       [method.to_s[0..-2], method.to_s[-1..-1]]
     else
       [method, nil]
     end
   end
end

usage_example.rb

class Foo

  extend Tracer

  def foo
    puts "inside foo"
  end

  trace :foo
end

irb(main):087:0> Foo.new.foo
called Foo#foo()
inside foo
Foo#foo => nil
=> nil