Finding if class method is called externally or internally

Question

class MyParent
  def self.foo
    if this_method_was_called_internally?
      puts "yay" 
    else
      puts "boo"
    end
  end
end

class MyLibrary < MyParent
  foo # yay
end

MyLibrary.foo # boo

Is this possible?

Answer 1

The simple answer is no. You can however play with caller, it gives you access to the call stack, much like an exception backtrace:

def this_method_was_called_internally?
  caller[1].include?(...)
end

(caller[1] would be the previous call, i.e. the method calling this_method...)

It's very hackish, and the information you get from caller may not be enough.

Please don't use this other than to experiment.

Answer 2

If you can afford a little modification of your code:

class MyParent
  def self.foo(scope)
    if scope == self
      puts "yay" 
    else
      puts "boo"
    end
  end
end

class MyLibrary < MyParent
  foo(self) # yay
end

MyLibrary.foo(self) # boo