Coredata 中的更新答案

【问题标题】：Update in CoredataCoredata 中的更新
【发布时间】：2015-12-28 11:26:26
【问题描述】：

我有一个设备实体，其中数据样本

data: {
    company = ddd;
    name = jje;
    version = dd;
})

我想更新公司等于 ddd 的名称。这是我的代码。请帮助

-(IBAction)update:(id)sender
{
    NSManagedObjectContext *managedObjectContext = [appdelegate managedObjectContext];
    NSEntityDescription *entityDescriptionDelegate = [NSEntityDescription entityForName:@"Device" inManagedObjectContext:managedObjectContext];
    NSFetchRequest *requestData = [[NSFetchRequest alloc] init];
        [requestData setReturnsObjectsAsFaults:NO];
    [requestData setEntity:entityDescriptionDelegate];
    NSError *error;
    NSArray *objectsArray = [managedObjectContext executeFetchRequest:requestData error:&error];

    for (NSManagedObject *object in objectsArray) {

        NSLog(@"%@",object);
        NSLog(@"%@",objectsArray);

    }

【问题讨论】：

标签： ios objective-c iphone core-data

【解决方案1】：

-(IBAction)update:(id)sender
 {
  NSManagedObjectContext *managedObjectContext = ((AppDelegate *)[[UIApplication sharedApplication] delegate]).managedObjectContext;
NSEntityDescription *entityDescriptionDelegate = [NSEntityDescription entityForName:@"Device" inManagedObjectContext:managedObjectContext];
  NSFetchRequest *requestData = [[NSFetchRequest alloc] init];
  [requestData setReturnsObjectsAsFaults:NO];
  [requestData setEntity:entityDescriptionDelegate];
  NSError *error;
  NSArray *objectsArray = [managedObjectContext executeFetchRequest:requestData error:&error];


  for (NSManagedObject *object in objectsArray) {
    [object setValue:@"Updated Name" forKey:@"name"];
    [object setValue:@"Updated version" forKey:@"version"];
  }


  if (![managedObjectContext save:&error]) {
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
  }
 }

【讨论】：

【解决方案2】：

希望对您有所帮助。将 YOUR_VALUE 文本更改为实际值

-(IBAction)update:(id)sender
{
    NSManagedObjectContext *managedObjectContext = [appdelegate managedObjectContext];
    NSEntityDescription *entityDescriptionDelegate = [NSEntityDescription entityForName:@"Device" inManagedObjectContext:managedObjectContext];
    NSFetchRequest *requestData = [[NSFetchRequest alloc] init];
    [requestData setReturnsObjectsAsFaults:NO];
    [requestData setEntity:entityDescriptionDelegate];
    [requestData setPredicate:[NSPredicate predicateWithFormat:@"company == YOUR_VALUE"]];

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

    for (Device *object in objectsArray) {
        object.name = @"YOUR_VALUE";
        object.version = @"YOUR_VALUE";

        [managedObjectContext save:&error];
    }
}

【讨论】：

for (Device *object in objectsArray) {
这一行的设备是什么。
您可以通过 Xcode 使用您的实体生成此对象。选择你的 .xcdatamodeld 文件，然后选择 Editor -> Create NSManagedObject Subclass...

【解决方案3】：

只需按如下方式更改for循环

 for (Device *object in objectsArray) {
            object. company = @"newName";
        }
 [self.managedObjectContext save:nil];

【讨论】：

什么是设备设备是我的实体名称
它的 entityName 有问题 [NSEntityDescription entityForName:@"Device" inManagedObjectContext:managedObjectContext]; NSFetchRequest *requestData = [[NSFetchRequest alloc] init]