在索引501處的獲取對象具有亂序部分名稱'JOURNAL OF APPLIED PHYSICS。對象必須按部分名稱排序'

Question

我有一個包含日記部分名稱的文章數據庫。一篇是「應用物理雜誌」，另一篇是「應用物理雜誌」。當我使用

[[NSSortDescriptor alloc] initWithKey:@"Journal" ascending:YES elector:@selector(caseInsensitiveCompare:)] 

來獲取數據，它給了我錯誤消息。

The fetched object at index 501 has an out of order section name 'JOURNAL OF APPLIED PHYSICS. Objects must be sorted by section name' 

我已經在使用不區分大小寫的比較，所以爲什麼這不起作用？幫幫我？

=======用於獲取數據======= 代碼

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 

NSEntityDescription *entity = [NSEntityDescription entityForName:@"Article" 
              inManagedObjectContext:SharedMOC]; 

[fetchRequest setEntity:entity]; 

NSSortDescriptor *journalSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Journal" 
                    ascending:ascending 
                     selector:@selector(caseInsensitiveCompare:)]; 

NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:journalSortDescriptor, nil]; 

[fetchRequest setSortDescriptors:sortDescriptors]; 

NSFetchedResultsController *a = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
                    managedObjectContext:SharedMOC 
                     sectionNameKeyPath:[self selectedSortSection] 
                       cacheName:cacheName]; 

Answer 1

我的直覺說，而不是：

[fetchRequest setSortDescriptors:[self getSortDescriptor]]; 

你應該寫：

[fetchRequest setSortDescriptors:sortDescriptors];