Question

我想存储文本字段中的数据。然后使用此数据填充视图控制器内标签中的文本。这可能吗？我已经弄乱了它，但似乎没有任何作用。有什么想法吗？这是我的两种方法......

- (IBAction)saveButton:(id)sender {
CoreDataStack *coreDataStack = [CoreDataStack defaultStack];
NSManagedObject *noteEntry = [NSEntityDescription insertNewObjectForEntityForName:@"Notes" inManagedObjectContext:coreDataStack.managedObjectContext];
[noteEntry setValue:_notesField.text forKey:@"notes"];

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




[coreDataStack saveContext];


}

这是我的观点做了加载方法：

- (void)viewDidLoad
{
[super viewDidLoad];


CoreDataStack *coreDataStack = [CoreDataStack defaultStack];
NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Notes"];
Notes *entry = [NSEntityDescription insertNewObjectForEntityForName:@"Notes" inManagedObjectContext:coreDataStack.managedObjectContext];

_outputLabel.text = entry.notes;

}

Answer 1

saveButton:方法中的代码似乎没问题。但是viewDidLoad方法中的代码似乎有误。您是否尝试执行以下操作？

- (void)viewDidLoad {
    [super viewDidLoad];

    CoreDataStack *coreDataStack = [CoreDataStack defaultStack];

    //First way to init your fetchRequest:
    NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Notes"];

    //Second way to init your fetchRequest:
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Notes" inManagedObjectContext:coreDataStack];
    [fetchRequest setEntity:entity];
    //Having a NSEntityDescription object can be usefull if you need to group your data, for example

    //Set some predicates, if necessary
    //Set some sortdescriptors, if necessary

    NSError *error;
    NSArray *resultsArray = [coreDataStack executeFetchRequest:request error:&error];

    NSLog(@"%@", resultsArray);
    _outputLabel.text = [[resultsArray firstObject] notes]; //if your array can only have one object
}

NSLog将为您提供获取阵列的结构（我无法猜测）。然后，您就可以设置_outputLabel.text。

Answer 2

@ user1966109的回答是完全正确的答案你正在寻找的。由于您需要在标签中显示文本，因此您需要设置谓词以获得单行。将谓词设置如下

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"value == abc"];//considerin abc is the word you are looking for.
request.predicate = predicate;
//then execute the query.

核心数据输入提取到标签中

2 个答案: