Defining “method_called”.. How do I make a hook method which gets called every time any function of a class gets called?

Question

I want to make a hook method which gets called everytime any function of a class gets called. I have tried method_added, but it executes only once at the time of class defin

Answer 1

method_added is there to run code when a new method has been added to the class; it doesn't report when a method has been called. (As you discovered.)

If you don't want to follow mikej's answer, here is a class that implements your specification:

#!/usr/bin/ruby

class Base
  def self.method_added(name)
    if /hook/.match(name.to_s) or method_defined?("#{name}_without_hook")
      return
    end
    hook = "def #{name}_hook\n p 'Method #{name} has been called'\n #{name}_without_hook\nend"
    self.class_eval(hook)

    a1 = "alias #{name}_without_hook #{name}"
    self.class_eval(a1)

    a2 = "alias #{name} #{name}_hook"
    self.class_eval(a2)
  end
  def a
    p "a called."
  end
  def b
    p "b called."
  end
end
t1 = Base.new
t1.a
t1.b
t1.a
t1.b

And output:

$ ./meta.rb
"Method a has been called"
"a called."
"Method b has been called"
"b called."
"Method a has been called"
"a called."
"Method b has been called"
"b called."