6

ガイはあなたが元気であることを願っています。

iPhone開発初心者です。コアデータを使用して簡単なアプリケーションを作成しています。アプリケーション中にデータを保存すると正常に動作し、データを取得すると正常に動作します。しかし、アプリケーションを再起動すると、すべてのデータが失われます。

アプリケーションの起動時に、ViewDidLoad 関数で、作業中のアプリケーションで取得したのと同じ関数でデータを取得しています。

データ保存方法：

    NSManagedObjectContext *context=[app managedObjectContext];
    Contacts *data=[NSEntityDescription insertNewObjectForEntityForName:@"Contacts" inManagedObjectContext:context];
    if(nameField.text.length <=0 || phoneField.text.length <=0 )
    {

        UIAlertView *alert=[[UIAlertView  alloc]initWithTitle:@"Warning!" message:@"Please enter some data." delegate:self cancelButtonTitle:@"Ok" otherButtonTitles: nil];
        [alert show];
    }
    else
    {
        data.name = nameField.text;
        data.phone = phoneField.text;
        NSLog(data.name);
        NSLog(data.phone);
        [self.navigationController popToRootViewControllerAnimated:YES];

    }

データの取得方法:

    NSEntityDescription *entity=[NSEntityDescription entityForName:@"Database" inManagedObjectContext:context];

    NSFetchRequest *fetchRequest=[[NSFetchRequest alloc]init];

    [fetchRequest setFetchBatchSize:20];

    [fetchRequest setEntity:entity];

    NSSortDescriptor *sorting = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];

    NSArray *sorted_Array=[NSArray arrayWithObject:sorting];

    [fetchRequest setSortDescriptors:sorted_Array];

    NSError *error;

    NSMutableArray *tArray=[[context executeFetchRequest:fetchRequest error:&error]mutableCopy];

    [self setArray:tArray];
    [self.tableView reloadData];

アプリ デリゲート コード

#import "ZAppDelegate.h"
#import "Contacts.h"

@implementation ZAppDelegate

@synthesize window = _window;
@synthesize managedObjectContext = __managedObjectContext;
@synthesize managedObjectModel = __managedObjectModel;
@synthesize persistentStoreCoordinator = __persistentStoreCoordinator;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.

    TableViewController *TVC=[[TableViewController alloc]init];

    TVC.MOcontext=self.managedObjectContext;

    UINavigationController *nvgc=[[UINavigationController alloc]initWithRootViewController:TVC];
    self.window.rootViewController=nvgc;


    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application
{
    /*
     Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
     Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
     */
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    /*
     Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
     If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
     */
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    /*
     Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
     */
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    /*
     Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
     */
}

- (void)applicationWillTerminate:(UIApplication *)application
{
    // Saves changes in the application's managed object context before the application terminates.
    [self saveContext];
}

- (void)saveContext
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil)
    {
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error])
        {
            /*
             Replace this implementation with code to handle the error appropriately.

             abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 
             */
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        } 
    }
}

#pragma mark - Core Data stack

/**
 Returns the managed object context for the application.
 If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
 */
- (NSManagedObjectContext *)managedObjectContext
{
    if (__managedObjectContext != nil)
    {
        return __managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil)
    {
        __managedObjectContext = [[NSManagedObjectContext alloc] init];
        [__managedObjectContext setPersistentStoreCoordinator:coordinator];
    }
    return __managedObjectContext;
}

/**
 Returns the managed object model for the application.
 If the model doesn't already exist, it is created from the application's model.
 */
- (NSManagedObjectModel *)managedObjectModel
{
    if (__managedObjectModel != nil)
    {
        return __managedObjectModel;
    }
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Diary" withExtension:@"momd"];
    __managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return __managedObjectModel;
}

/**
 Returns the persistent store coordinator for the application.
 If the coordinator doesn't already exist, it is created and the application's store added to it.
 */
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (__persistentStoreCoordinator != nil)
    {
        return __persistentStoreCoordinator;
    }

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Diary.sqlite"];

    NSError *error = nil;
    __persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error])
    {
        /*
         Replace this implementation with code to handle the error appropriately.

         abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 

         Typical reasons for an error here include:
         * The persistent store is not accessible;
         * The schema for the persistent store is incompatible with current managed object model.
         Check the error message to determine what the actual problem was.


         If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.

         If you encounter schema incompatibility errors during development, you can reduce their frequency by:
         * Simply deleting the existing store:
         [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]

         * Performing automatic lightweight migration by passing the following dictionary as the options parameter: 
         [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

         Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.

         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }    

    return __persistentStoreCoordinator;
}

#pragma mark - Application's Documents directory

/**
 Returns the URL to the application's Documents directory.
 */
- (NSURL *)applicationDocumentsDirectory
{
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}

@end

ここで何か問題がありますか？良い回答が早く得られることを願っています。

4

5 に答える 5

5

アプリケーションのライフ サイクルのある時点で、 を呼び出す必要があります。そうsaveしNSManagedObjectContextないと、変更が に保存されませんNSPersistentStore。たとえば、アプリケーション デリゲートのapplicationDidEnterBackground:メソッドです。

NSError *saveError = nil;
if( ![[self managedObjectContext] save:&saveError] ) {
   //  deal with error...
}

Apple テンプレートのように、アプリケーション デリゲートが Core Data スタックをセットアップして維持すると仮定しています...

于 2012-09-19T12:29:44.813 に答える
4

AppDelegate で:

- (void)applicationWillTerminate:(UIApplication *)application
{
  // Saves changes in the application's managed object context before the application terminates.
  [self saveContext];
}

Xcode のテンプレートの以前のバージョンにある可能-saveContext性があります。-save

さらに、他のクラスで-saveorメソッドを呼び出すことができます。-saveContent

[(AppDelegate *)[UIApplication sharedApplication] saveContext];
于 2012-09-19T14:18:49.693 に答える
0

このコンテキストを保存する必要があります
CoreDataManager * context = [CoreDataManager sharedInstance];
...
...
...
...
...
...
[コンテキスト保存コンテキスト];

于 2015-02-02T14:29:48.347 に答える
0

NSManagedObjectContext はスクラッチ パッドを提供します。オブジェクトで好きなことを行うことができますが、最後に保存する必要があります。NSManagedObjectContext に加えた変更は、保存するまで一時的なものです。これをメソッドの最後に追加してみてください：

if (![context save:&error]) {
 NSLog(@"Couldn't save: %@", error);
}
于 2014-10-17T05:59:00.193 に答える
0

コードのどこにセーブを入れているのかわかりません。管理コンテキストに保存するように指示する必要があります。どこでそれを行うかは、アプリとデザインによって異なります。既にアプリのどこかにあると思われる場合は、いくつかの NSLog を追加してデバッグするか、デバッガー ツールを使用して実際にコードにステップ インします。

それは簡単な修正です。幸運を。

于 2012-09-19T13:08:20.837 に答える