Question

I’ve just starting out with obj-c and I created 2 files, a .h and a .m file. The .h file is..

#import <Foundation/Foundation.h>

@interface CardUnit : NSObject
{
@private 
    NSString *_name;
    NSString *_gold;
}
@property (nonatomic, assign) NSString *name;
@property (nonatomic, assign) NSString *gold;
@end

and the .m file is

#import "CardUnit.h"

@implementation CardUnit

@synthesize gold  = _gold;
@synthesize name = _name;

@end

But it’s giving me 2 errors on the @synthesize lines, which are…

“Existing ivar “_gold” for property gold with assign attribute must be __unsafe retained” and the same for name.

Answer 1

From the error i see you are using ARC, Automatic Reference Counting .

Basically you can get rid of all the @synthesize statements and even the private declarations of the ivar’s name and gold is not necessary.

All you need is the CardUnit.h to be like this :

@interface CardUnit : NSObject

  @property (assign) NSString *name;
  @property (assign) NSString *gold;

@end

The Xcode compiler will take care of the rest.

See also this reply on SO