警告添加方法为

Question

我一直在使用的核心数据，那么复制所有的核心数据，我需要过到我目前的项目应用程序代理应用程序委托代码创​​建了一个新项目的核心数据的应用程序代理..

我的appdelegate.m现在看起来像这样。

// 
// AppDelegate.m 
// testingcoredata 
// 
// Created by iMac on 18/11/11. 
// Copyright (c) 2011 __MyCompanyName__. All rights reserved. 
// 

#import "AppDelegate.h" 

#import "MasterViewController.h" 

@implementation AppDelegate 

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

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

    MasterViewController *masterViewController = [[MasterViewController alloc] initWithNibName:@"MasterViewController" bundle:nil]; 
    self.navigationController = [[UINavigationController alloc] initWithRootViewController:masterViewController]; 
    masterViewController.managedObjectContext = self.managedObjectContext; 
    self.window.rootViewController = self.navigationController; 
    [self.window makeKeyAndVisible]; 
    return YES; 
} 

- (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:@"testingcoredata" 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:@"testingcoredata.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 

我的问题如下 是在URLForResource代码换货的这部分反映了我创建了我xcdatamodeld的名字吗？

NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"testingcoredata" withExtension:@"momd"]; 

随着URLByAppendingPathComponent：我必须创建一个名为Code.sqlite SQLite数据库，或者这个自动完成对我的核心数据的代码？

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

这种方法的目的究竟是什么？

applicationDocumentsDirectory 

Answer 1

1. URLForResource表示在束中的momd文件的URI的路径。
2. URLByAppendingPathComponent - 您提供的代码将创建名为Code.sqlite的数据库。你可以自由地将名字改为任何你想要的。
3. applicationDocumentsDirectory方法在应用沙箱返回路径的文档文件夹