Class

Classes in Ruby are first-class objects—each is an instance of class Class.

When a new class is created (typically using class Name … end), an object of type Class is created and assigned to a global constant (Name in this case). When Name.new is called to create a new object, the new method in Class is run by default. This can be demonstrated by overriding new in Class:

class Class
   alias oldNew  new
   def new(*args)
     print "Creating a new ", self.name, "\n"
     oldNew(*args)
   end
 end

 class Name
 end

 n = Name.new

produces:

Creating a new Name

Classes, modules, and objects are interrelated. In the diagram that follows, the vertical arrows represent inheritance, and the parentheses meta-classes. All metaclasses are instances of the class `Class’.

                         +------------------+
                         |                  |
           Object---->(Object)              |
            ^  ^        ^  ^                |
            |  |        |  |                |
            |  |  +-----+  +---------+      |
            |  |  |                  |      |
            |  +-----------+         |      |
            |     |        |         |      |
     +------+     |     Module--->(Module)  |
     |            |        ^         ^      |
OtherClass-->(OtherClass)  |         |      |
                           |         |      |
                         Class---->(Class)  |
                           ^                |
                           |                |
                           +----------------+