TIL #3 - Method look-up in Ruby

I stumbled across this TIL because I've been looking up advanced topics in a bid to learn new things and deepen my knowledge of Ruby & Rails.

Everything in Ruby is an object.
All Ruby objects have an ancestor chain. BasicObject is always at the end of that chain.
All classes have a Class ancestor.
Class inherits from Module which means every class is sort of a module. "Sort of" because unlike actual modules you can't mixin classes. Module adds in instantiation, properties etc to classes.

Method lookup in Rails is possible because of a few fields all Ruby objects, classes, and modules have.

objects

class: A pointer to the class object of the object. For example, for an Fish class, calling the class method returns Class.
iv_tbl (Instance Variable Table): a hashtable containing the instance variables of the object.

classes, modules

m_tbl (Method Table) - A hashtable containing all the class or module's instance methods.
super - A pointer to the class or module's superclass (direct ancestor). You can lookup the ancestors of an object by calling the ancestors method on that object.

Ruby follows the object's class pointer and checks its method table (m_tbl) for a match.
If there's no match, it follows the object's super pointer and checks its method table for a match. Ruby continues up the super ancestor chain, looking into each ancestor's method table for a match.
If there is still no match, Ruby invokes method_missing on the original object. FYI, method_missing is a method so it'll undergo this lookup process too until it is found and invoked.