Question

[newVehicle setValue: _txtFieldVehicleNumber.text forKey:@"number"];

[newVehicle setValue: lblFuelType.text forKey:@"fueltype"];

[newVehicle setValue: lblFuelUnit.text forKey:@"fuelunit"];

[newVehicle setValue: lblDistanceUnit.text forKey:@"distanceunit"];

我想更新名为“Vehicle”的核心数据实体，对于该实体，我有几个属性，我想更新其中一些但不是全部，当我从实体中选择特定属性时。那我该怎么办？

Answer 1

您可以执行以下操作（近似代码。实现错误处理和检查语法）。

NSFetchRequest *fetchRequest=[NSFetchRequest fetchRequestWithEntityName:@"Vehicle"];
NSPredicate *predicate=[NSPredicate predicateWithFormat:@"vehicle_id==%@",vehicle_id]; // If required to fetch specific vehicle
fetchRequest.predicate=predicate;
Vehicle *newVehicle=[[self.managedObjectContext executeFetchRequest:fetchRequest error:nil] lastObject];

[newVehicle setValue: _txtFieldVehicleNumber.text forKey:@"number"];

[newVehicle setValue: lblFuelType.text forKey:@"fueltype"];

[newVehicle setValue: lblFuelUnit.text forKey:@"fuelunit"];

[newVehicle setValue: lblDistanceUnit.text forKey:@"distanceunit"];

[self.managedObjectContext save:nil]

Answer 2

从核心数据中获取实体：

VVdAppDelegate *delegate = (VVdAppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *managedObjectContext = [delegate managedObjectContext];
NSEntityDescription *entityDescriptionDelegate = [NSEntityDescription entityForName:@"entityName" inManagedObjectContext:managedObjectContext];
NSFetchRequest *requestData = [[NSFetchRequest alloc] init];
[requestData setEntity:entityDescriptionDelegate];
NSError *error;

如果有多个NSManagedObject

NSArray *objectsArray = [managedObjectContext executeFetchRequest:requestData error:&error];

for (NSManagedObject *object in objectsArray) {

        // Here update values of every object

}

// And save values to core data
[managedObjectContext save:&error];

如何更新核心数据输入的值

2 个答案: