The document discusses Ruby's object model and relationships between different types of objects. It explains that all objects in Ruby inherit from the Object class and have a class. Classes are also objects that have a class of Class. The document provides examples of using kind_of? to check an object's type and defines relationships between core classes like Integer, Fixnum and String. It illustrates how modules can be included to add methods and explains singleton classes for objects and classes.

1. Understanding Ruby’s Object Model Chris Pine July 10, 2003

13. Wrong Mental Picture Object class Classes Subclasses objects

17. Superclass Relationships Object Module Class String Integer Fixnum

18. Class Relationships Object Module String Integer Fixnum 5 ' hi ' Class

20. Right Mental Picture Object Module Class String Integer Fixnum 5 ' hi '

24. Singleton Classes (classes) Polygon Triangle hypotenuse area largest new Class Polygon(S) ? ? ? ?

25. Polygon Triangle hypotenuse area largest new Class Poly(S) Tri(S) Object Obj(S) Class(S) Mod(S) Module