编辑 CoreData 值

Question

我一直在尝试将一些数据从 tableview 传递到 editviewcontroller，以便能够对其进行编辑和保存，但我并不走运

我不知道如何将这些值从所选行传递到编辑视图，然后保存新值

这是我的代码：

- (NSManagedObjectContext *)managedObjectContext{
NSManagedObjectContext *context = nil;
id delegate = [[UIApplication sharedApplication] delegate];
if ([delegate performSelector:@selector(managedObjectContext)]) {
    context = [delegate managedObjectContext];
}
return context;
}
-(IBAction)atras:(id)sender{
MenuViewController *m=[[MenuViewController alloc] initWithNibName:nil bundle:nil];
[self presentViewController:m animated:YES completion:nil];

}
-(IBAction)guardar:(id)sender{
NuevaTareaViewController *n=[[NuevaTareaViewController alloc] initWithNibName:nil bundle:nil];
[self presentViewController:n animated:YES completion:nil];

}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];

// Fetch the devices from persistent data store
NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Tareas"];
self.tareas = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy];

[tableView reloadData];
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 1;
}

 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return self.tareas.count;
}

 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell;

cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}


// Configure the cell...
NSManagedObject *materia = [self.tareas objectAtIndex:indexPath.row];
[cell.textLabel setText:[NSString stringWithFormat:@"%@", [materia valueForKey:@"nombre"]]];
cell.textLabel.textColor=[UIColor whiteColor];
cell.textLabel.font=[UIFont fontWithName:@"Chalkduster" size:(16)];

NSString *detalle=[NSString stringWithFormat:@"%@: Toca para ver los Detalles",[materia valueForKey:@"materia"]];
[cell.detailTextLabel setText:detalle];
cell.detailTextLabel.textColor=[UIColor whiteColor];
cell.detailTextLabel.font=[UIFont fontWithName:@"Chalkduster" size:(12)];

return cell;
}
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
// Return NO if you do not want the specified item to be editable.
return YES;
}


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

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

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

    // Remove device from table view
    [self.tareas removeObjectAtIndex:indexPath.row];
    [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
}
}
- (void)viewDidLoad
{
[super viewDidLoad];

// Uncomment the following line to preserve selection between presentations.
// self.clearsSelectionOnViewWillAppear = NO;

// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem;
}

 - (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

NSManagedObject *materia = [self.tareas objectAtIndex:indexPath.row];

NSString *perfil_activo = [materia valueForKey:@"descripcion"];
NSUserDefaults *defs=[NSUserDefaults standardUserDefaults];
//[defs setObject:perfil_activo forKey:@"perfil_activo"];

[tableView deselectRowAtIndexPath:indexPath animated:YES];

UIAlertView *a=[[UIAlertView alloc] initWithTitle:@"texto" message:perfil_activo delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil, nil];
[a show];

}

谢谢 圣地亚哥

Answer 1

你想获取当前选中的对象。

NSIndex selectedRow = self.tableView.selectedRow;

在你的 tableview 中使用这个索引： NSManagedObject *selectedObject = [self.tableView objectAtIndex:selectedRow]

在您的NuevaTareaViewController 中应该有一个属性： NSManagoedObjectContext Tarea

如果是这样，那么你可以这样做：

-(IBAction)guardar:(id)sender {

NSIndex selectedRow = self.tableView.selectedRow;
NSManagedObject *selectedObject = [self.tableView objectAtIndex:selectedRow];

NuevaTareaViewController *n=[[NuevaTareaViewController alloc] initWithNibName:nil     bundle:nil];

[n setManagedObjectContext:self.context];
[n setTarea:selectedObject];

[self presentViewController:n animated:YES completion:nil];

}

您可以将托管对象上下文保存在您的 NuevaTareaViewController 中。

话虽如此，请阅读NSFetchedResultsController 和Storyboard Segues，您可能会发现它们很有帮助。