A refactoring of TraceCalls (Metaprogramming - Programming Ruby 1.9 & 2.0, 4th edition)

trace_calls.rb

module TraceCalls
  def self.included(base)
    [base, base.singleton_class].each do |klass|
      klass.instance_methods(false).each do |existing_method|
        wrap(klass, existing_method)
      end
    end

    def base.method_added(method)
      TraceCalls.run_method_added(self, method, __method__)
    end

    def base.singleton_method_added(method)
      TraceCalls.run_method_added(self.singleton_class, method, __method__)
    end
  end

  def self.run_method_added(klass, method, method_added)
    klass.instance_eval do
      return if method == method_added || @trace_calls_internal

      @trace_calls_internal = true
      TraceCalls.wrap(klass, method)
      @trace_calls_internal = false
    end
  end

  def self.wrap(klass, method)
    klass.instance_eval do
      method_object = klass.instance_method(method)

      define_method(method) do |*args, &block|
        puts "==> calling #{method} with #{args.inspect} on #{self}"
        result = method_object.bind(self).call(*args, &block)
        puts "<== #{method} returned #{result.inspect}"
        result
      end
    end
  end
end

class Example
  def one(arg)
    puts "One called with #{arg}"
  end

  def self.hi
    puts 'hi'
  end
end

ex1 = Example.new
ex1.one("Hello")
Example.hi

class Example
  include TraceCalls

  def two(arg1, arg2)
    arg1 + arg2
  end

  def self.three(arg)
    puts "Three called with #{arg}"
    3
  end
end

ex1.one("Goodbye")
Example.hi
puts ex1.two(4, 5)
puts Example.three("something")