Question

我有一些ViewControllers。在我登录的第一个LoginViewController中，我创建了newEntity。通过单击“登录”按钮，我通过谓词“login”进行获取并为此newEntity提取分配。 AppDelegate.h为Core Data创建了一些东西。在LoginViewController中，我在.h中有下一个字符串：

@class AppDelegate;
...
@property (strong, nonatomic) AppDelegate *appMeDelegate;
@property (strong, nonatomic) NSManagedObjectContext *context;
...

在LoginViewController.m中

#import "AppDelegate.h"
...
@synthesize ... appMeDelegate, context;
...
//I have login button where i compare login and password in 
//UITextFields with that in Core Data and if it is 
//all right i load fetch for user with his login
-(IBAction)login:
{
appMeDelegate = (AppDelegate *) [[UIApplication sharedApplication]delegate];
context = appMeDelegate.managedObjectContext;
NSFetchRequest * fetchRequest = [[NSFetchRequest alloc]init];
NSPredicate *predicateMe = [NSPredicate predicateWithFormat:@"login==%@",login.text];
fetchRequest.predicate = predicateMe;
... //then I create newEntity }
//next method for saving
-(void)saving
{
NSError *error = nil;
if (![context save:&error]) {
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
}}

然后在其他ViewController中我使用newEntity但无法保存它

- (void)viewDidLoad
{
[super viewDidLoad];
NSData *newdata = [NSData dataWithData:self.loginViewController.newEntity.photo];
photoArray = [NSMutableArray arrayWithArray:
[NSKeyedUnarchiver unarchiveObjectWithData:newdata]];}

-(IBAction)save
 {  [photoArray addObject:myImage];
NSData *newData = [NSKeyedArchiver archivedDataWithRootObject:photoArray];
[self.loginViewController.newEntity setValue:newData forKey:@"photo"];
[self.loginViewController saving];

但没有结果，也没有保存实体的变化

Answer 1

您可以使用类似的方法来保存您的managedDocument上下文

    [self.managedDocument saveToURL: self.managedDocument.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:^(BOOL success) {
    if (completionHandler) completionHandler(success);
}];

修改对不起，刚看到您显然没有使用NSManagedDocument（您应该查看）。

不要这样做：

[self.loginViewController saving];

像以前那样做：

appMeDelegate = (AppDelegate *) [[UIApplication sharedApplication]delegate]; NSManagedObjectContext *context = appMeDelegate.managedObjectContext; [context save: &error];

编辑后将实体保存在核心数据中

1 个答案: