我们可以利用
objc_setAssociatedObject
objc_getAssociatedObject
来为类动态添加和获取属性static char dynamicKey;
NSArray *array = @[@"4", @"5", @"6"];
NSString *dymaicString = @"动态添加属性";
objc_setAssociatedObject(array, &dynamicKey, dymaicString, OBJC_ASSOCIATION_RETAIN);
NSString *associatedObject = (NSString *)objc_getAssociatedObject(array, &dynamicKey);
NSLog(@"%@",associatedObject);