Race condition

gistfile1.txt

@interface StringContainer : NSObject

- (instancetype)initWithString:(NSString *)string;
@property (nonatomic, unsafe_unretained) NSString *string;

@end

@implementation StringContainer

- (instancetype)initWithString:(NSString *)string {
    self = [super init];
    if (self) {
        self.string = string;
    }
    return self;
}


@interface Some : NSObject {
    NSString *stringProp;
}

@end

@end

@implementation Test

- (instancetype)init {
    self = [super init];
    if (self) {
        dispatch_async(dispatch_get_global_queue(0, 0), ^{
            [self test];
        });
    }
    return self;
}

- (void)test {
    for(int i = 0; i < 1000; i++) {
        dispatch_async(dispatch_get_global_queue(0, 0), ^() {
            stringProp = [[StringContainer alloc] initWithString:[[NSString alloc] initWithFormat:@"%d", i]];
        });
        dispatch_async(dispatch_get_global_queue(0, 0), ^() {
            [self print:stringProp];
        });
    }
}

- (void)print:(StringContainer * __unsafe_unretained)string {
    NSLog(@"%@", string.string);
}

@end