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)  |
                            ^                |
                            |                |
                            +----------------+