What is an Objective-C “class continuation”?

Question

I can\'t quite figure out what I have seen referred to as an Objective-C \"class continuation\". Is this / are these…

1. Ivar(s) declar

Answer 1

A continuation class is what Apple calls a class extension. I have seen clang call them "continuation class" and gcc uses "class continuation".

Compile this in clang or gcc:

@interface Foo : NSObject
@property int a;
@end

@interface Foo()
@property float a;
@end

... and you will get errors with the funny names.

To answer the rest of your question:

1. What is the scope, lifetime, and usage case for such a thing?

Extensions are used to declare the private interface for a class. You can also use it to redeclare (refine) public property declarations.

2. Is this an ARC-specific "feature"?

NO.

3. Are there specific runtime, or other requirements for their use?

Class Extensions are a compile time concept and do not require a special runtime. Of course they do require a compiler that supports them (both clang and gcc do in current versions).

4. Is this an appropriate place to create an @property, as well? And why would this be a better place for setting ivars or properties than, say, the @interface file / declaration?

YES. Because you might want to have private properties.

5. Why do people complicate discussions by using such specific terminology - that seems NOT to exist in any official documentation (that I could find)?

Well, you know... I'd also prefer if the whole world spoke English, but for the time being I'm happy with the fact that I had to learn it in school.