Anyone can point out a documentation or a detailed discussion using @class. I've been using this but haven't really fully understood it. I want to learn more about it and fully understand it.
Thank you in advance.
+4
A:
// 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.
Richard J. Ross III
2010-09-06 17:43:17
+1 good point about circular references. That really illustrates the difference between `@class` and `#import`
e.James
2010-09-06 17:48:21
+1 for same reasons, fixed your syntax error though.
jer
2010-09-06 18:00:13
That's not what he's talking about. Consider you define two classes, A and B, each having an ivar to one another. You will have to declare one as 'id' or use a forward declaration because of the circular nature, gcc just acts stupidly in such cases. Also I generally recommend not #import'ng files just for class definitions if you do not need access to its members, there's no need—Use `@class` instead.
jer
2010-09-06 18:15:24
@jer: unless I'm completely mistaken, that's exactly what he's talking about. *A* and *B* in your example would be *class* and *reference* in his.
e.James
2010-09-07 16:06:37
+3
A:
@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.
e.James
2010-09-06 17:43:35
+2
A:
@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
ennuikiller
2010-09-06 17:45:54