Ruby - Using class_eval to define methods

Question

I\'m doing the SaaS Stanford class, trying to do Part 5 of this assignment

I\'m having a really hard time grasping this concept, this is what I\'ve attempted to do:<

Answer 1

You must notice that #{attr_name}_history is a instance variable, so use @ before, like @foo in the class below

def #{attr_name}=value, #{attr_name}= is the method name, value is parameter, same as def func parameter

def #{attr_name}=value
  (!defined? @#{attr_name}_history) ? @#{attr_name}_history = [nil, value] : @#{attr_name}_history << value
end