帶fetchOffset的NSFetchRequest不會返回預期的結果

Question

我試圖從Core Data獲取「分頁」實體時遇到了一些奇怪的事情。

這裏是我使用的抓取代碼：

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); 

而且這裏是日誌：

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 

在這個測試中我有6項爲 「用戶」。

我在做什麼錯？

謝謝

Answer 1

您的日誌表明一切都按預期工作。

恭喜！

Answer 2

發現了問題：

fetchRequest.fetchOffset = offset*limit;