Introduction

Ruby's Object Model was influenced by Smalltalk. The Smalltalk object model follows a set of simple rules that are uniformly applied. The rules are:

Rule 1

Everything is an object.

Rule 2

Every object is an instance of a class.

Rule 3

Every class has a superclass.

Rule 4

Everything happens by sending messages.

Rule 5

Method look-up follows the inheritance chain.

Ruby Object Model

In Ruby, Rule 1 is not applicable. We have seen that everything is not an object. We can say:

• Everything in the inheritance hierarchy is an Object.
• Receiver and Sender in a message sending interaction are objects.
• Every class is an object. In other words, every class is an instance of a Ruby built-in class called Class.

We have already discussed the Rule 3 and 4 in the previous section. In this section, you will learn about Rule 2 and 5.