[iOS] Core Data 代码速查表

来源：互联网发布：python数据挖掘招聘编辑：程序博客网时间：2024/06/05 16:05

文中代码均来源于：http://www.appcoda.com/introduction-to-core-data/

希望学习 Core Data 的同学不要错过：）以下是我个人记录的一些常用代码片段。

有一个 Entity：Device，有三个属性：company、name、version。

1.获取 context 的方法：

- (NSManagedObjectContext *)managedObjectContext {    NSManagedObjectContext *context = nil;    id delegate = [[UIApplication sharedApplication] delegate];    if ([delegate performSelector:@selector(managedObjectContext)]) {        context = [delegate managedObjectContext];    }    return context;}

2.增加一条数据：

    NSManagedObjectContext *context = [self managedObjectContext];        // Create a new managed object    NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:@"Device" inManagedObjectContext:context];    [newDevice setValue:self.nameTextField.text forKey:@"name"];    [newDevice setValue:self.versionTextField.text forKey:@"version"];    [newDevice setValue:self.companyTextField.text forKey:@"company"];        NSError *error = nil;    // Save the object to persistent store    if (![context save:&error]) {        NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);    }

3.删除一条数据：

NSManagedObjectContext *context = [self managedObjectContext];// Delete object from database[context deleteObject:[self.devices objectAtIndex:indexPath.row]];NSError *error = nil;if (![context save:&error]) {    NSLog(@"Can't Delete! %@ %@", error, [error localizedDescription]);    return;}

4.修改一条数据：

NSManagedObjectContext *context = [self managedObjectContext];    // Update existing device[self.device setValue:self.nameTextField.text forKey:@"name"];[self.device setValue:self.versionTextField.text forKey:@"version"];[self.device setValue:self.companyTextField.text forKey:@"company"];NSError *error = nil;// Save the object to persistent storeif (![context save:&error]) {    NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);}

5. 查询一堆数据：

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

0 0