核心数据更新

Question

我有一个项目，有一对多的关系。我正在尝试更新核心数据。我有核心数据

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若要添加和更新，请使用以下代码

NSManagedObjectContext *context = [self managedObjectContext];

if (self.contactdb) {
    // Update existing device
    [self.contactdb setValue:self.name.text forKey:@"name"];

   //------------- ???? --------------------

} else {
    // Create a new device
    NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:@"Name" inManagedObjectContext:context];
    [newDevice setValue:self.name.text forKey:@"name"];

    for (int i = 0 ; i< appDelegate.TimeOfReceipt.count; i++) {

        NSManagedObject *timeinday = [NSEntityDescription insertNewObjectForEntityForName:@"Timeinday" inManagedObjectContext:context];

        TimeCell *p1 = [appDelegate.TimeOfReceipt objectAtIndex:i];

        [timeinday setValue:p1.dateOfTime forKey:@"timeinday"];
        [timeinday setValue:[NSNumber numberWithInt:i] forKey:@"index"];
        [timeinday setValue:newDevice forKey:@"name"];

    }

}
NSError *error = nil;
// Save the object to persistent store
if (![context save:&error]) {
    NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);
}

我如何更新时辰？

Answer 1

NSManagedObjectContext *context = твой контекст;

NSPredicate *pred = [NSPredicate predicateWithFormat:@"name.name like[cd] %@",@"Нужный name у Name"];

NSEntityDescription *ed = [NSEntityDescription entityForName:@"Timeindays" inManagedObjectContext:context];

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:ed];
[fetchRequest setPredicate:pred];

fetchRequest.includesPropertyValues = NO;
fetchRequest.includesSubentities = NO;


NSError *error;
NSArray *items = [context executeFetchRequest:fetchRequest error:&error];

if (error) {
    NSLog(@"Error requesting items from Core Data: %@", [error localizedDescription]);
}

for (NSManagedObject *managedObject in items) {
    [context deleteObject:managedObject];
}

if (![context save:&error]) {
    NSLog(@"Error deleting %@ - error:%@", ed, [error localizedDescription]);
}

Илипросто

//Выбери нужный Name, потом: 

for (NSManagedObject *managedObject in name.timeinday) {
    [context deleteObject:managedObject];
}

if (![context save:&error]) {
    NSLog(@"Error deleting %@ - error:%@", ed, [error localizedDescription]);
}

Answer 2

您最好在Xcode中创建托管对象子类，因为它将添加许多在集成到多个关系时可以使用的适当类型的方法。然后，使用这些方法而不是setValue:forKey:。

在你的情况下，虽然你应该这样做，但你的关系是1：-多，所以你可以设置1结尾：

[newDevice setValue:timeinday forKey:@"timeinday"];