retain strong 和 copy 讨论，有建议的的童鞋请留言

标签：retain strong 和 cop

否则weak引用为野指针，会出现问题

这里说strong 有copy的功能是错误的哦。实验例子

@interface AppDelegate : UIResponder <UIApplicationDelegate>
{
    NSString *retainStr;
    NSString *copStr;
    NSString *strongStr;
}

@property (retain, nonatomic) NSString *retainStr;
@property (strong, nonatomic) NSString *strongStr;
@property (copy, nonatomic) NSString *copStr;

@end

    NSMutableString *newStr = [NSMutableString stringWithFormat:@"abcd"];
    self.retainStr = newStr;
    self.strongStr = newStr;
    self.copStr = newStr;
    
    [newStr appendString:@"123"];
    
    NSLog(@"retain sting:%@", self.retainStr);
    NSLog(@"strong string:%@", self.strongStr);
    NSLog(@"copy string:%@", self.copStr);

输出结果：
2014-05-02 13:31:17.660 TestMultipleThreadDownload[552:60b] retain sting:abcd123
2014-05-02 13:31:17.662 TestMultipleThreadDownload[552:60b] strong string:abcd123
2014-05-02 13:31:17.663 TestMultipleThreadDownload[552:60b] copy string:abcd

retain strong 和 copy 讨论，有建议的的童鞋请留言

标签：retain strong 和 cop

原文地址：http://blog.csdn.net/u011374880/article/details/42463037