iOS / iPhone ARC内存管理

Question

 __weak NSString *strin = [[NSString alloc] initWithFormat:@"hey"] ;

    NSLog(@"weak %@",strin); //returns weak (null)

__weak NSString *strin =@"hey";

NSLog(@"weak %@",strin); //returns weak hey

What is the difference between both the snippets. Why the second is returning the value when weak is assigned ?

Answer 1

这是因为@"hey"是一个常量字符串文字，它将永远存在，而对第一个（已分配）字符串的弱引用不足以使其保持活动状态。

Answer 2

Check below snap and you will get your answer your self.