"Object is the root of Ruby's class hierarchy. Its methods are available to all classes unless explicitly overridden."
Wouldn't Class class be at the root of the class hierarchy? After all, look at this: 1.9.2p290 :006 > Object.instance_of? Class => true Object is an instance of class, after all we can use one of Class' instance methods on Object: 1.9.2p290 :017 > Object.new => #<Object:0x007faad047ecd0> But Class is not instance of Object: 1.9.2p290 :007 > Class.instance_of? Object => false 1.9.2p290 :008 > defined? Class => "constant" 1.9.2p290 :009 > Class.class => Class 1.9.2p290 :010 > Object.class => Class Class is an instance of Class. That is, Class is an instance of itself. And therefore "Class" just is (kind of like the idea if something stems from something else, how was the very first thing created - it just was). Class is just an internal construct, built part of the language for templating. So Object is a constant that represents an object allocated in memory. When it's methods are searched for it looks up the scope chain, first at the singleton class (just in case any methods are extended on Object) and after that, it looks at its immediate parent which is Class, and hence that's why we can say Object.new, since Class class defines "new". Now this is the interesting part. There obviously is a difference between Object and Class. As already stated, Object is an instance of Class and therefore inherits from Clas, not visa versa. The difference is made clear as shown below: We have a constant "A". We want that constant to be a class, so we do it easily: A = Class.new We know that A is a class because we can run A.new. However, when we create an object: B = Object.new This fails: 1.9.2p290 :007 > B.new NoMethodError: undefined method `new' for #<Object:0x007ff597d27820> When we instantiate B, the instance gets B's instance methods. But why doesn't it get Class's instance method (new)? B inherits from Object which inherits from Class. It should have looked up scope chain until it reached Class, since Object is an instance of Class and therefore inherits from it. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
