Question

使用核心数据填充我的表格视图。我没有得到的是如何从核心数据中删除单个条目。

以下是我正在使用的代码：

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

if (tableView == favouritesTable) {
    cellValue = [licensePlateArray objectAtIndex:indexPath.row];
} else { // handle search results table view
    cellValue = [filteredListItems objectAtIndex:indexPath.row];
}

static NSString *CellIdentifier = @"vlCell";

VehicleListCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if (cell == nil) {

    NSLog(@"Cell Created");

    NSArray *nibObjects = [[NSBundle mainBundle] loadNibNamed:@"VehicleListCell" owner:nil options:nil];

    for (id currentObject in nibObjects) {
        if ([currentObject isKindOfClass:[VehicleListCell class]]) {
            cell = (VehicleListCell *)currentObject;
        }
    }

    UILongPressGestureRecognizer *pressRecongnizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(tableCellPressed:)];
    pressRecongnizer.minimumPressDuration = 0.5f;
    [cell addGestureRecognizer:pressRecongnizer];
    [pressRecongnizer release];
}

cell.textLabel.font = [UIFont systemFontOfSize:10];

Favouritesdata *favdata = [licensePlateArray objectAtIndex:indexPath.row];

[[cell ignition] setImage:[UIImage imageNamed:@"ignition.png"]];
[[cell direction] setImage:[UIImage imageNamed:@"south.png"]];

cell.licPlate.text = [favdata licenseplate];

NSLog(@"cellvalue for cellforRow: %@", cell.licPlate.text);

return cell;}

在UILongPressGestureRecognizer的方法中：

- (void)tableCellPressed:(UILongPressGestureRecognizer *)recognizer{

if (recognizer.state != UIGestureRecognizerStateBegan) {
    return;
}

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:nil delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles: nil] ;

[alert addButtonWithTitle:@"Remove from Favourites"];
[alert addButtonWithTitle:@"Take to Map"];

[alert show];}

在警报视图方法中：

-(void)alertView:(UIAlertView *)alert clickedButtonAtIndex:(NSInteger)buttonIndex {

NSString *title = [alert buttonTitleAtIndex:buttonIndex];

NSManagedObjectContext *contextFav = [app managedObjectContext];
Favouritesdata * favourites = [NSEntityDescription insertNewObjectForEntityForName:@"Favouritesdata" inManagedObjectContext:contextFav];

if([title isEqualToString:@"Remove from Favourites"])
{
    NSLog(@"cellValueForLongPress: %@", cellValueForLongPress);


    if (cellValueForLongPress <= 0) {

        NSLog(@"No data to delete");

    }
    else {

        favourites.licenseplate = cellValueForLongPress;
    }

    [alert dismissWithClickedButtonIndex:0 animated:YES];
}
else if([title isEqualToString:@"Take to Map"])
{
    NSLog(@"Go to MapView");
}

NSError *error;

if (![context save:&error]) {
    NSLog(@"Error Occured");
}}

Answer 1

如果要从CoreData存储中删除托管对象，则应该：

引用NSManagedObjectContext，您将删除对象：context
您要删除的NSManagedObject的引用：object

然后删除对象非常简单：

[context deleteObject:object];

你应该知道

要删除的行的索引，例如i。
从您的阵列中检索它：NSObject *object = [licensePlateArray objectAtIndex:i];
从db：[context deleteObject：object];
将其从数组中删除：[licensePlateArray removeObject：object];

Answer 2

您必须识别NSManagedObject，然后在managedObjectContext上调用 deleteObject 。然后，此对象将从核心数据中删除。

但是你必须提供一种机制来“以某种方式”获取特定tableview行后面的对象。

通过表iPhone删除核心数据单一条目

2 个答案: