iPhone取出由核心數據的數據並顯示在表

Question

錯誤：「原因：「+ entityForName：未能找到NSManagedObjectModel的實體名稱爲」

我創建使用標籤式應用程序的新項目。我創建了多個選項卡，然後在我的delegate.h文件中添加核心數據函數，如下所示。

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

    - (void)saveContext; 
    - (NSURL *)applicationDocumentsDirectory; 

現在我改變了delegate.m文件，如下

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

    #pragma mark - 
    #pragma mark Application lifecycle 

    - (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(); 
       } 
      } 
     } 

     - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
      { 
      // Override point for customization after application launch. 

       return YES; 
       } 

     - (void)applicationWillResignActive:(UIApplication *)application 
      { 

      } 

     - (void)applicationDidEnterBackground:(UIApplication *)application 
      { 

      } 

     - (void)applicationWillEnterForeground:(UIApplication *)application 
     { 

      } 

     - (void)applicationDidBecomeActive:(UIApplication *)application 
     { 
     } 

     - (void)applicationWillTerminate:(UIApplication *)application 
     { 

     [self saveContext]; 

      } 



    #pragma mark - Core Data stack 


    - (NSManagedObjectContext *)managedObjectContext 
     { 
      if (__managedObjectContext != nil) { 
       return __managedObjectContext; 
       } 

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


     - (NSManagedObjectModel *)managedObjectModel 
      { 
      if (__managedObjectModel != nil) { 
        return __managedObjectModel; 
        } 
       NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"myapp" withExtension:@"momd"]; 
      __managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL]; 
       return __managedObjectModel; 
       } 

     - (NSPersistentStoreCoordinator *)persistentStoreCoordinator 
      { 
      if (__persistentStoreCoordinator != nil) { 
       return __persistentStoreCoordinator; 
       } 

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

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

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

     return __persistentStoreCoordinator; 
     } 

    #pragma mark - Application's Documents directory 

     - (NSURL *)applicationDocumentsDirectory 
     { 
     return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory   inDomains:NSUserDomainMask] lastObject]; 
     } 

     @end 

我有我在哪裏添加數據視圖控制器，我能夠獲取數據以及但是當我做同樣從表中獲取數據我得到一個錯誤，它無法找到coredata表。 我myappTableViewController.h文件如下：

  #import <UIKit/UIKit.h> 
      #import "myappAppDelegate.h" 

      @interface myappTableViewController : UITableViewController 


      @property(nonatomic,retain)NSManagedObjectContext *managedObjectContext; 
      @property(nonatomic,retain)NSArray *arr; 

     -(void)getData; 

      @end 

在myappTableViewController.m文件添加以下代碼：

-(void)getData{ 

      NSEntityDescription *entity = [NSEntityDescription entityForName:@"Data" inManagedObjectContext:managedObjectContext]; 

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

      [request setFetchBatchSize:20]; 

      [request setEntity:entity]; 

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

      NSArray *newArray = [NSArray arrayWithObject:sort]; 

      [request setSortDescriptors:newArray]; 

      NSError *error; 

      NSMutableArray *results = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy]; 

      [self setArr:results]; 

      [self.tableView reloadData]; 


      } 

和我打電話[個體經營的getData]在ViewDidLoad中。和合成

  @synthesize managedObjectContext,arr; 


     - (void)viewDidLoad 
      { 
      [super viewDidLoad]; 

      [self getData]; 
      } 

現在有一些地方，我需要做的事情與管理的ObjectContext ..我想我只是缺少一行代碼的地方..

Prerna

Answer 1

你必須創建你的xcdatamodeld。根據你的代碼，它應該被稱爲myapp.xcdatamodeld。這個模型應該包含你想要獲取的實體，你的情況是Data。