带有fetchOffset的NSFetchRequest不会返回预期的结果

Question

我在尝试从Core Data获取“分页”实体时遇到了一些奇怪的事情。

以下是我用于获取的代码：

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"User" 
                                          inManagedObjectContext:self.managedObjectContext];
fetchRequest.predicate = [NSPredicate predicateWithFormat:@"userIdentifier beginswith[cd] %@ AND selected == 1",userIdentifier];
fetchRequest.fetchOffset = offset;
fetchRequest.fetchLimit = limit;
[fetchRequest setEntity:entity];
NSLog(@"offset %d limit %d",fetchRequest.fetchOffset,fetchRequest.fetchLimit);

NSError *requestError = nil;
NSArray *items = [self.managedObjectContext executeFetchRequest:fetchRequest
                                                          error:&requestError];
NSLog(@"fetched items count = %d",items.count);

以下是日志：

2013-01-31 16:01:28.127 offset 0 limit 100
2013-01-31 16:01:28.128 fetched items count = 6
2013-01-31 16:01:40.533 offset 1 limit 100
2013-01-31 16:01:40.535 fetched items count = 5
2013-01-31 16:01:53.029 offset 2 limit 100
2013-01-31 16:01:53.032 fetched items count = 4
2013-01-31 16:01:55.468 offset 3 limit 100
2013-01-31 16:01:55.470 fetched items count = 3
2013-01-31 16:02:00.776 offset 4 limit 100
2013-01-31 16:02:00.779 fetched items count = 2
2013-01-31 16:02:02.325 offset 5 limit 100
2013-01-31 16:02:02.328 fetched items count = 1
2013-01-31 16:02:03.837 offset 6 limit 100
2013-01-31 16:02:03.839 fetched items count = 0
2013-01-31 16:02:07.714 offset 6 limit 100
2013-01-31 16:02:07.717 fetched items count = 0

对于此测试，我有6个“用户”条目。

我做错了什么？

由于

Answer 1

您的日志表明一切正常。

恭喜！

Answer 2

发现问题：

fetchRequest.fetchOffset = offset*limit;