Question

I was trying to write my first method_missing override when I kept running into (edited) stack level too deep errors. The main culprit seemed to be trying to utilize an instance attribute. For instance if ‘self’ was a instance of the User class then checking for something like:

def method_missing(name)
  if self.name
    # do stuff
  end
end

Would seg fault. I spent a long time on this but ended up giving up. There must be something I’m not understanding about accessing it.

Edit

My apologies, Andrew is correct, I am getting Stack Level too deep errors. With this in mind, what is the appropriate (if any) way to access the instances attribute values?

Answer 1

You can potentially rectify this problem by ensuring that self.name actually exists:

def method_missing(name)
  if self.respond_to?(:name) && self.name
    # do stuff
  end
end

Note this may not work if your class inherits from anything Railsy (e.g. ActiveRecord::Base), since it overrides respond_to?.

If you are in a Railsy class, your method missing should call super, lest you lose a lot of the “magic” ActiveRecord methods (including, probably, self.name itself):

def method_missing(name, *args, &block)
  if name_is_something_i_should_handle_here
    # do your stuff
  else
    super(name, *args, block) # call parent's method_missing
  end
end

Obviously you should replace name_is_something_i_should_handle_here with the appropriate logic.

You may also wish to consider using dynamic method creation instead of method_missing.