I'm somewhat confused about the Ruby object hierarchy. Every class that I define is an instance of the class Class, and Class has the hierarchy Class < Module < Object < BasicObject. If I define a class A, then A has the hierarchy A < Object < BasicObject. But if A is an instance of the class Class, should the superclass of A not be Module, like in the first hierarchy above? A's class is Class, so it would make sense to me that it should follow the top one!!
on 2012-12-14 16:54
on 2012-12-14 18:06
On Fri, Dec 14, 2012 at 4:54 PM, Joz Private <firstname.lastname@example.org> wrote: > it would make sense to me that it should follow the top one!! No. A is a class and as such has a hierarchy. But since everything in Ruby is an object, even classes are. An object is always an instance of a class. In this case A is an instance of Class. And Class has its own hierarchy. So you have A < Object < BasicObject L -instanceOf- Class < Module < Object < BasicObject Kind regards robert
on 2012-12-14 22:15
Hi, I think your problem is that you confuse "instance of" and "subclass of". Yes, A is an *instance* of Class. But it's not a *subclass* of Class. So there's no direct relation to Module.
on 2012-12-14 22:20
If you have these classes defined: class Parent end class A < Parent end Here is what the basic hierarchy looks like: +--------+ +--------+ | Basic | | Basic | | Object | | Object | | | | | +--------+ +--------+ ^ ^ | | | | +--------+ +--------+ | | | | | Object | | Object | | | | | +--------+ +--------+ ^ ^ | | | | +--------+ +--------+ | | | | | Parent | | Module | | | | | +--------+ +--------+ ^ ^ | | | | +-----+ +-------+ a = -----> | A | -----> | Class | A.new | | | | +-----+ +-------+ Think about going from an object to the right into its class, and then up the hierarchy to the superclass.
on 2012-12-15 08:37
7stud -- wrote in post #1089134: > > Think about going from an object to the right into its class, and then > up the hierarchy to the superclass. > How about this instead: an object's class is to the right of it in the diagram, and an object's superclass is above it. The object 'a' is not a class, so it has no superclass and nothing appears above it in the diagram. The object A's class is to its right, i.e. Class, and A's superclass is above A, i.e. Parent. Now what about Class? It's a class because this works: MyClass = Class.new and because Class is a class, it is has to be an instance of Class. So Class's *class* is Class, and as shown in the diagram Class's superclass is Module because we know from the ruby docs that Class inherits from Module. You defined the class A yourself, so unless you wrote: class A < Module end or class Parent < Module end class A < Parent end ...then A doesn't inherit from Module.