将代码配置为迁移的持久存储的位置

Question

我已经在App Store上创建并分发给许多客户的Mac App，我需要在Core Data Model中添加一个属性。我阅读了Apple提供的文档，可用here。

但是，它提供了此代码块以启用自动迁移：

NSError *error;
NSPersistentStoreCoordinator *psc = <#The coordinator#>;
NSURL *storeURL = <#The URL of a persistent store#>;
NSDictionary *optionsDictionary =
    [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES]
                    forKey:NSMigratePersistentStoresAutomaticallyOption];

NSPersistentStore *store = [psc addPersistentStoreWithType:<#Store type#>
                                configuration:<#Configuration or nil#>
                                URL:storeURL
                                options:optionsDictionary
                                error:&error];

..我不知道该把它放在哪里。有人提到（在另一个线程中）它进入PersistentStoreCoordinator，但是，我只是使用了默认的Cocoa App Template，并启用了“使用核心数据存储”。我不得不创建自己的AppDelegate，从来没有看到任何关于PersistentStoreCoordinator的东西（但仍然没有。我试过创建一个新的应用程序只是为了检查）。这里有什么帮助？我是Cocoa的新手，但我的应用程序完全正常，没有PersistentStoreCoordinator，这就是为什么我还没有实现一个..我确实有一个我创建的AppDelegate，但是当我把这个代码放在那里时会引发很多错误。帮助：/

EDIT（for nick）：这是新代码：

我的头文件：

Answer 1

在这里：核心数据相关的标题和方法。

应用程序代理标题 - 核心数据相关部分

@interface CoreDataFirstStepsAppDelegate : NSObject <UIApplicationDelegate> 
{    
     // ...
@private
    NSManagedObjectContext *managedObjectContext_;
    NSManagedObjectModel *managedObjectModel_;
    NSPersistentStoreCoordinator *persistentStoreCoordinator_;
}

// ...

@property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;
@property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;

应用代表实施 - 核心数据相关部分

/**
 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_;
    }
    NSString *modelPath = [[NSBundle mainBundle] pathForResource:@"CoreDataFirstSteps" ofType:@"momd"];
    NSURL *modelURL = [NSURL fileURLWithPath:modelPath];
    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:@"CoreDataFirstSteps.sqlite"];

    NSError *error = nil;
    persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![persistentStoreCoordinator_ addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {

        NSError *error;
        NSURL *storeURL = storeURL;
        NSPersistentStoreCoordinator *psc = persistentStoreCoordinator_;
        NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                                 [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

        if (![psc addPersistentStoreWithType:NSSQLiteStoreType
                               configuration:nil
                                         URL:storeURL
                                     options:options 
                                       error:&error]) 
        {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }       
    }    

    return persistentStoreCoordinator_;
}

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