iphone - NSMutableArray 和 NSDictionary 错误

Question

我有一个名为 SubList 的 NSMutableArray，其中包含 262 个元素。每个对象都是一个 NSDictionary!

这段代码就像一个魅力!

for (NSDictionary *element in listSub){
    [cell.textLabel setText:[element objectForKey:@"title"]];  

}  

但是如果我尝试使用此代码，我会收到 SIGBART 错误!

NSDictionary * element = [listSub objectAtIndex:[indexPath row]];

[cell.textLabel setText:[element objectForKey:@"title"]];

那么问题出在哪里呢？

*编辑问题出在这一行

NSDictionary * element = [listSub objectAtIndex:[indexPath row]];

这是描述由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因:“-[__NSCFSet objectAtIndex:]:无法识别的选择器发送到实例 0x89a8d90”谢谢

**编辑这是 listSub 的输出!

listSub: {(
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/Web Programming";
                label = "Web Programming";
            }
        );
        firstitemmsec = 1265885595862;
        id = "feed/http://feeds.feedburner.com/FamousBloggers";
        sortid = A11327DE;
        title = "Famous Bloggers";
    },
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/Hacking";
                label = Hacking;
            }
        );
        firstitemmsec = 1241258413829;
        htmlUrl = "http://backtrack-italia.blogspot.com/";
        id = "feed/http://feeds2.feedburner.com/BackTrackItalia";
        sortid = E8A04F76;
        title = "Back Track Italia";
    },
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/Hacking";
                label = Hacking;
            }
        );
        firstitemmsec = 1245376992188;
        htmlUrl = "http://www.offensive-security.com";
        id = "feed/http://www.offensive-security.com/blog/feed/";
        sortid = 92F57555;
        title = "BackTrack Information Security Distribution";
    },
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/iOS Developer";
                label = "iOS Developer";
            }
        );
        firstitemmsec = 1296830392306;
        htmlUrl = "http://amix.dk/Main/";
        id = "feed/http://feeds.feedburner.com/amixdk";
        sortid = 110C52C3;
        title = "amix.dk blog";
    },
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/Apple News";
                label = "Apple News";
            }
        );
        firstitemmsec = 1285261350202;
        htmlUrl = "http://www.appletvhacks.net";
        id = "feed/http://www.appletvhacks.net/feed/";
        sortid = 81125D2E;
        title = "Apple TV Hacks";
    },
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/Apple News";
                label = "Apple News";
            }
        );
        firstitemmsec = 1293230300220;
        htmlUrl = "http://www.appletvitalia.it";
        id = "feed/http://www.appletvitalia.it/feed/";
        sortid = 892FE61C;
        title = "Apple Tv Italia";
    },
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/Apple News";
                label = "Apple News";
            }
        );
        firstitemmsec = 1270115980935;
        htmlUrl = "http://www.appleecious.com";
        id = "feed/http://feeds2.feedburner.com/appleecious";
        sortid = 00B5AFC2;
        title = Appleecious;
    },
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/Hacking";
                label = Hacking;
            }
        );
        firstitemmsec = 1258495136927;
        htmlUrl = "http://www.rawseo.com/news";
        id = "feed/http://www.rawseo.com/news/feed/";
        sortid = D6766911;
        title = "A blend of programming and seo";
    },
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/Seo e Web Marketing";
                label = "Seo e Web Marketing";
            }
        );
        firstitemmsec = 1233684720758;
        htmlUrl = "http://it-adsense.blogspot.com/";
        id = "feed/http://it-adsense.blogspot.com/atom.xml";
        sortid = 9FB570ED;
        title = "AdSense Blog-Italiano";
    },
        {
        categories =         (
        );
        firstitemmsec = 1277627346000;
        htmlUrl = "http://aext.net";
        id = "feed/http://feeds.feedburner.com/aextnet";
        sortid = 70800CFE;
        title = "AEXT.NET NET MAGAZINE";
    },
        {
        categories =         (
        );
        firstitemmsec = 1217001547735;
        htmlUrl = "http://www.alessandroscoscia.it";
        id = "feed/http://feeds.feedburner.com/alessandroscoscia";
        sortid = 51CB8E6E;
        title = "Alessandro Scoscia";
    },
        {
        categories =         (
                        {
                id = "user/14761688561595773457/label/iOS Developer";
                label = "iOS Developer";
            }
        );
...

我确定它不是 NSSet。

现在我发布用于填充数组的代码。

 NSError *error;
    NSURLResponse *response;
    NSData  *dataReply = [NSURLConnection sendSynchronousRequest:theRequest returningResponse:&response error:&error];
    NSString *string = [[NSString alloc] initWithData:dataReply encoding:NSASCIIStringEncoding];
    NSLog(@"testing %@",string);


    SBJsonParser *vol= [[SBJsonParser alloc]init];
    if (string) {
        NSArray *feeds = [vol objectWithString:string error:nil];
        NSDictionary *results = [string JSONValue];
        NSArray *subs = [results valueForKey:@"subscriptions"];

        for (NSDictionary *iscrizione in subs){

            [subscriptions addObject:iscrizione];

        }

这是另一个类的一部分，如果我尝试做这样的事情，也在我的代码的这一部分中:NSDictionary * element = [listSub objectAtIndex:0];NSLog([元素 objectForKey:@"title"]);

如果我尝试这样的循环，我会得到同样的错误

for (NSDictionary *element in listSub){
    [cell.textLabel setText:[element objectForKey:@"title"]];  

} 

一切正常，没有 NSSet 错误。这让我发疯!

Answer 1

问题可能是 listSub 没有正确保留，因此已经被释放。内存现在被重新使用，并且该地址处的对象现在是一个 __NSCFSet，它不会响应 objectAtIndex:。

请注意，由诸如 [NSMutableArray arrayWithXXX] 之类的便利类方法返回的自动释放对象应保留，并且仅在不再需要时释放。确保保留它们的最佳方法是声明一个 @property(retain) NSArray *subList、@synthesize 并使用 self.subList 在所有情况下，除了在 dealloc 中。

添加

有人建议创建 subList 的方法返回一个集合而不是数组。如果是这样的话，答案开头的简单循环也将不起作用。这就是为什么我发现 subList 最初不太可能是 NSSet，更有可能的是该数组被过度释放和释放，并且内存重新用于 >NSSet.

请按照那些想要帮助您的人的要求去做。

添加行

NSLog(@"listSub: %@", listSub);

在设置listSub的地方，也在错误行之前。然后查看错误日志中显示的内容并告诉我们。