@class May I know the proper use of this

Anyone can point out a documentation or a detailed discussion using @class. I've been using this but haven't really fully un开发者_运维技巧derstood it. I want to learn more about it and fully understand it.

Thank you in advance.

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@class is used to declare a class. Essentially telling the compiler: "Hey, there is a class with this name somewhere in the source code. The definition will come later, but let me use its name as a pointer type for now."

See also:
developer.apple.com
SO: Class vs Import
MacRumors

Note: As pointed out by Richard J. Ross III, the @class keyword allows for circular references (when two classes both depend on each-other) without breaking the build.

---

// header.h
#import <Foundation/Foundation.h>
@class reference;

@interface class
...
@end
// implementation.m
#import "header.h"
#import "reference.h"

@implementation class
...
@end

you use this when you have a class that is referenced circularly between multiple files, and you import the header that contains the class described by the @class directive, and you can safely refer to the class circularly.

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@class is used as a forward declaration typically in .h files. What it does is it says that a class named ClassName actually exists without having to import and read the ClassName.h file since it, mot probably, will be imported by the .m file