Public – can be called from anywhere
Private – The method cannot be called outside class scope. The object can only send the message to itself
ex: the baker has bake method as public but break_eggs is private
Protected – You can call an object’s protected methods as long as the default object self is an instance of the same class as the object whose method you’re calling
ex: with n protected method, c1 can ask c2 to execute c2.n, because c1 and c2 are both instances of the same class
And last but not least:
- Inheritance: Subclasses inherit the method-access rules of their superclass
if “class D < C”, then D will exhibit the same access behaviour as instances of C
reference: http://www.amazon.com/Ruby-Rails-Techniques-Developers/dp/1932394699