if（objc_getAssociatedObject（self，＆Key））對於零對象返回true

Question

如何測試objc_getAssociatedObject是nil？以下說元素不是nil，但關聯的對象從來沒有被設置過，也沒有被訪問過。

static char orderedElementKey = 11; 

if (objc_getAssociatedObject(self, &orderedElementKey) != nil) 
{ 
    NSLog(@"element is not nil"); 
    return objc_getAssociatedObject(self, &orderedElementKey); 
} 
NSLog(@"elelement was nil !"); 

Answer 1

static char orderedElementKey = 11; 
//objc_setAssociatedObject(self, &orderedElementKey, @"value", OBJC_ASSOCIATION_RETAIN); 

if (objc_getAssociatedObject(self, &orderedElementKey) != nil) 
{ 
    NSLog(@"Element: %@", objc_getAssociatedObject(self, &orderedElementKey)); 
} 
else 
{ 
    NSLog(@"element nil !"); 
} 

打印 「元素零！」同時刪除對objc_setAssociatedObject()的評論將打印「元素：值」。你的代碼有什麼不同？