致命异常：NSGenericException ***集合＆lt; __ NSArrayM：0x17165f620＆gt;在被列举时被突变

Question

我从MutableArray中检索项目时遇到致命异常。应用程序崩溃了。

错误：

    Fatal Exception: NSGenericException
    *** Collection <__NSArrayM: 0x17165f620> was mutated while being enumerated.
     Raw Text
0 CoreFoundation    __exceptionPreprocess
1 libobjc.A.dylib   objc_exception_throw
2 CoreFoundation    -[NSException name]
3 BroadCastApp      GPBroadCastService.m line 624
                    -[GPBroadCastService getSubscribedItemFromBroadcastedGroup:]

代码：

- (id)getSubscribedItemFromBroadcastedGroup:(id)group
{
    id item = nil;
    NSArray *broadcastedGroupItems = [self getBroadcasetedGroupItems];//Returns MutableArray

    for (item in [broadcastedGroupItems copy]) {
        if ([[item valueForKey:@"groupId"] isEqualToString:group.groupId]) 
        {
            break;
        }
    }
    return item;
}