Example trait usage.

Traits.m

#import <Foundation/Foundation.h>

#define trait(NAME) protocol NAME;\
@interface id_##NAME @end \
typedef id_##NAME<NAME> NAME; \
@protocol NAME

#define trait_implementation(NAME) \
interface NAME##_impl : NSObject<NAME>\
- (NAME *) asTrait$;\
@end \
@implementation NAME##_impl \
- (NAME *) asTrait$ { return (NAME*)self; }\

@trait(SomeInterface)

@property (nonatomic, retain) NSString* test;

- (void)printTest;

@end


@trait_implementation(SomeInterface)

@synthesize test;

- (void)printTest
{
    NSLog(@"Test is: %@", self.test);
}

@end

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        
        SomeInterface* testObject = [SomeInterface_impl new].asTrait$;
        
        testObject.test = @"Check";
        [testObject printTest];
        
    }
    return 0;
}

http://cl.ly/image/3R0h2f31292a/Снимок%20экрана%202014-05-06%20в%2001.13.09.png