objective-c - 带搜索的 NSFetchedResultsController

Question

过滤数据的最佳做法是什么NSFetchedResultsController？每次搜索栏的文本更改时，我是否需要重新初始化它？

我正在使用一个UISearchDisplayControllers并且我正在实施：

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString;

谢谢。

Answer 1

Guy的答案代码与问题有何不同？据我猜测， filterContentForSearchText:scope 方法是由 shouldReload 方法调用的吗？

无论如何，这是我在 CoreDataBooks 示例中添加的一些类似代码以包含搜索。在 IB 中为 CoreDataBooks 示例添加一个搜索显示控制器。然后我将代码添加到 RootViewController.m 如下：

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString {
 NSInteger searchOption = controller.searchBar.selectedScopeButtonIndex;
 return [self searchDisplayController:controller shouldReloadTableForSearchString:searchString searchScope:searchOption];
}

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchScope:(NSInteger)searchOption {
 NSString* searchString = controller.searchBar.text;
 return [self searchDisplayController:controller shouldReloadTableForSearchString:searchString searchScope:searchOption];
}

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString*)searchString searchScope:(NSInteger)searchOption {

 NSPredicate *predicate = nil;
 if ([searchString length])
  if (searchOption == 0) // full text, in my implementation.  Other scope button titles are "Author", "Title"
   predicate = [NSPredicate predicateWithFormat:@"title contains[cd] %@ OR author contains[cd] %@", searchString, searchString];
  else
   // docs say keys are case insensitive, but apparently not so.
   predicate = [NSPredicate predicateWithFormat:@"%K contains[cd] %@", [[controller.searchBar.scopeButtonTitles objectAtIndex:searchOption] lowercaseString], searchString];
 [fetchedResultsController.fetchRequest setPredicate:predicate];

    NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error]) {
  NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
  abort();
    }           

 return YES;
}

PS。为了回答 Vivas，它使用 UISearchDisplayController 自动创建一个新的表格视图来覆盖过滤列表。您可以检查正在使用的 tableView，如文档中所示，但在最简单的设置中，它可以正常工作，因为 fetchedResultsController 要么在搜索的表格视图中显示过滤版本，要么在表格视图中显示所有数据。

Answer 2

显然这是一个更好的方法：

- (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope
{
    self.savedSearchTerm = searchText;

    freshData = NO;
    if (searchText !=nil)
    {
            NSPredicate *predicate =[NSPredicate predicateWithFormat:@"name contains[cd] %@", searchText];
            [fetchedResultsController.fetchRequest setPredicate:predicate];
    }
    else
    {
            NSPredicate *predicate =[NSPredicate predicateWithFormat:@"All"];
            [fetchedResultsController.fetchRequest setPredicate:predicate];
    }

    NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error]) {
            // Handle error
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            exit(-1);  // Fail
    }           

    [self.tableView reloadData];

    //    [searchBar resignFirstResponder];   
    //    [_shadeView setAlpha:0.0f];

 }