What is an isa instance variable?

Question

The NSObject class reference refers to the "isa instance variable", which

initialized by a data structure that describes the class

can someone explain what i should know about this isa instance variable? What is this good for? What does it mean? It sounds like a norm, for example, DIN, ISO, etc .; Any idea what it is?

Answer 1

It is used to determine the inheritance path of a class. Formally:

, , . ( NSObject), isa, . . - Objective-C GNUstep Base: Objective-C

isa OOP IS-A, , :

IS-A .
IS-A.

, isa , , IS-A .

Answer 2

Objective-C. , . , Objective-C.

.