无论是否有搜索文本匹配，UISearchBar 都显示“无结果”

Question

我正在使用表格视图搜索栏来搜索我的核心数据内容并在UITableView 中显示匹配的内容。

问题是，如果您输入与某些内容匹配的搜索文本，TableView 是否显示“无结果”。

谁能告诉我为什么？

TableViewController 代码：

 (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSManagedObjectContext *context = [self managedObjectContext];

    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete object from database
        [context deleteObject:[self.cart objectAtIndex:indexPath.row]];

        NSError *error = nil;
        if (![context save:&error]) {
            NSLog(@"Can't Delete! %@ %@", error, [error localizedDescription]);
            return;
        }

        // Remove device from table view
        [self.cart removeObjectAtIndex:indexPath.row];
        [self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }
}

//Searchbar
#pragma mark Content Filtering
-(void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope {
    // Update the filtered array based on the search text and scope.
    // Remove all objects from the filtered search array
    [self.filteredProductsArray removeAllObjects];
    // Filter the array using NSPredicate
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"Cart.cartProductName contains[c] %@",searchText];
    filteredProductsArray = [NSMutableArray arrayWithArray:[cartProducts filteredArrayUsingPredicate:predicate]];
}

#pragma mark - UISearchDisplayController Delegate Methods
-(BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString {
    // Tells the table data source to reload when text changes
    [self filterContentForSearchText:searchString scope:
     [[self.searchDisplayController.searchBar scopeButtonTitles] objectAtIndex:[self.searchDisplayController.searchBar selectedScopeButtonIndex]]];
    // Return YES to cause the search result table view to be reloaded.
    return YES;
}

-(BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchScope:(NSInteger)searchOption {
    // Tells the table data source to reload when scope bar selection changes
    [self filterContentForSearchText:self.searchDisplayController.searchBar.text scope:
     [[self.searchDisplayController.searchBar scopeButtonTitles] objectAtIndex:searchOption]];
    // Return YES to cause the search result table view to be reloaded.
    return YES;
}

核心数据内容在 Cart.h 中，属性为 cartProductName，即 NSString。

更新：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    // Configure the cell...
    NSManagedObject *device = nil;
    if (tableView == self.searchDisplayController.searchResultsTableView)
        {device = [filteredProductsArray objectAtIndex:indexPath.row];}
    else
        {device = [self.cart objectAtIndex:indexPath.row]; }

    if (cell.accessoryView == nil) {
        // Only configure the Checkbox control once.
        cell.accessoryView = [[Checkbox alloc] initWithFrame:CGRectMake(0, 0, 25, 43)];
        cell.accessoryView.opaque = NO;
        cell.backgroundColor = [UIColor clearColor];

       [(Checkbox*)cell.accessoryView addTarget:self action:@selector(checkBoxTapped:forEvent:) forControlEvents:UIControlEventValueChanged];

    [cell.textLabel setText:[NSString stringWithFormat:@"%@", [device valueForKey:@"cartProductName"]]];
     //[(Checkbox*)cell.accessoryView setChecked: [((Cart*)device).checked boolValue]];

    //Accessibility

    [self updateAccessibilityForCell:cell];

return cell;
}
    return nil;
}

更新：CartTableViewController.m：

#import "CartViewController.h"
#import "Checkbox.h"
#import "Cart.h"


@interface CartViewController ()
@property (strong) NSMutableArray *cart;

@end

@implementation CartViewController {
    NSArray *cartProducts;
}

@synthesize filteredProductsArray;
@synthesize searchBar;

Answer 1

您提供了一些细节来了解问题所在，但我猜您的 -(void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope 应该是这样的：

[self.filteredProductsArray removeAllObjects];

NSFetchRequest *fetchRequest = // set up the fetch request for your Cart entity here...
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"cartProductName contains[cd] %@", searchText];
fetchRequest.predicate = predicate;

NSError *error = nil;
NSArray *results = [[self managedObjectContext] executeFetchRequest:fetchRequest error:&error];
if (results == nil) {
    // handle error here...
}

[self.filteredProductsArray addObjectsFromArray:results];

可以在Searching in UITableView 找到一个关于如何实现此目标的非常好的示例。

性能考虑。当使用cd 时，研究会比不使用它慢。所以，你可以直接使用contains。

希望对您有所帮助。