我有一个在OS3 +下正常运行的应用程序。但它在OS4下不起作用。我收到以下错误消息:
'NSFetchedResultsController不支持更改跟踪和 使用NSDictionaryResultType'
获取请求
这对这里的任何人都响了吗?
- (NSFetchedResultsController *)fetchedResultsController {
if (fetchedResultsController != nil) {
return fetchedResultsController;
}
/*
Set up the fetched results controller.
*/
// Create the fetch request for the entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:@"myEntity" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:myEntity];
[fetchRequest setResultType:NSDictionaryResultType];
[fetchRequest setPropertiesToFetch :[NSArray arrayWithObjects:@"FIELD1",@"FIELD2",@"FIELD3",@"FIELD4",@"FIELD5",nil]];
// Setting unique values
[fetchRequest setReturnsDistinctResults:YES];
// Edit the sort key as appropriate.
NSSortDescriptor *initialDescriptor = [[NSSortDescriptor alloc] initWithKey:@"FIELD1" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:initialDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
// Edit the section name key path and cache name if appropriate.
// nil for section name key path means "no sections".
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:@"FIELD1" cacheName:@"myCache"];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
[aFetchedResultsController release];
[fetchRequest release];
[initialDescriptor release];
[sortDescriptors release];
return fetchedResultsController;
}
提前致谢。
答案 0 :(得分:14)
错误指的是您尝试获取NSDictionary
结果,但随后也期望获取的结果控制器监视更改。由于更改只会通过NSManagedObjects
传播,因此获取的结果控制器无法再执行其工作。
使用NSManagedObjectResultType
不起作用,因为setPropertiesToFetch:不再适用。相反,在结果集已知之后,您必须执行自己的某些合并,这将很难用于获取的结果控制器。
最佳答案是不为提取的结果控制器设置缓存名称或委托,在这种情况下它将not perform any change tracking。