帶搜索的NSFetchedResultsController

Question

過濾NSFetchedResultsController數據的最佳做法是什麼？ 每次搜索欄的文本更改時，是否需要重新初始化它？

我使用的是UISearchDisplayControllers和我執行：

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

THX。

Answer 1

如何是蓋伊的答案代碼問題有什麼不同？據我猜測，filterContentForSearchText：scope方法是由shouldReload方法調用的？

無論如何，下面是我在CoreDataBooks示例中添加的一些類似代碼，以包含搜索。 CoreDataBooks示例在IB中添加Search Display Controller。然後我將代碼添加到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來回答Vivas，它會自動創建一個新的表格視圖，用於覆蓋已過濾的列表。您可以按照文檔中所示檢查正在使用哪個tableView，但是在最簡單的設置中，它可以正常工作，因爲fetchedResultsController在搜索的表視圖中顯示過濾版本或顯示錶視圖中的所有數據。

Answer 2

Appearantly這是一個更好的辦法：

- (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]; 

}