带搜索的NSFetchedResultsController

Question

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

我使用的是UISearchDisplayControllers和我执行：

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

THX。

Answer 1

如何是盖伊的答案代码问题有什么不同？据我猜测，filterContentForSearchText：scope方法是由shouldReload方法调用的？

无论如何，下面是我在CoreDataBooks示例中添加的一些类似代码，以包含搜索。 CoreDataBooks示例在IB中添加Search Display Controller。然后我将代码添加到RootViewController.m中，如下所示：

- (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。要使用UISearchDisplayController来回答Vivas，它会自动创建一个新的表格视图，用于覆盖已过滤的列表。您可以按照文档中所示检查正在使用哪个tableView，但是在最简单的设置中，它可以正常工作，因为fetchedResultsController在搜索的表视图中显示过滤版本或显示表视图中的所有数据。

Answer 2

Appearantly这是一个更好的办法：

- (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]; 

}