objective-c - 对核心数据中的特定部分进行排序

Question

我正在使用 NSFetchedResultsController 来填充我的应用程序的 tableView，它是按部分分组的(在这种情况下，我的核心数据对象中的类别属性)我想手动重新排序该部分，而不是按字母顺序。

下面是我到目前为止所做的代码

- (NSFetchedResultsController *)fetchedResultsController {

if (_fetchedResultsController != nil) {
    return _fetchedResultsController;
}

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription 
                               entityForName:@"Media" inManagedObjectContext:_context];
[fetchRequest setEntity:entity];

NSSortDescriptor *sort = [[NSSortDescriptor alloc] 
                          initWithKey:@"category" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

[fetchRequest setFetchBatchSize:20];

NSFetchedResultsController *theFetchedResultsController = 
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
                                    managedObjectContext:_context sectionNameKeyPath:@"category" 
                                               cacheName:@"Root"];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;

return _fetchedResultsController;    

}

提前致谢!

Answer 1

如果任务是提供部分的自定义顺序，那么您可以子类化 NSFetchedResultsController 并实现

- (NSInteger)sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)sectionIndex;

如果需要的话

@property (nonatomic, readonly) NSArray *sectionIndexTitles;
- (NSString *)sectionIndexTitleForSectionName:(NSString *)sectionName;