Question

我想创建一个使用Core Data的iphone应用程序。据我所知，只有master-detail应用程序模板才能让我选择使用Core Data。但它创建了表视图。

我想要使用的是视图控制器而不是表视图控制器。我无法将核心数据与单一视图应用程序模板一起使用。

我应该采用哪种方式来克服这个问题？

感谢。

Answer 1

您应该意识到CoreData是一个未绑定到任何UIKit组件（如UITableView）的框架。您可以在任何类型的应用程序中自由使用它。您所要做的就是创建管理CoreData操作的单例类，并将CoreData.framework添加到项目中。

这是我的DataAccessLayer模板：

DataAccessLayer.h

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
@interface DataAccessLayer : NSObject

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

+ (DataAccessLayer *)sharedInstance;
- (void)saveContext;

@end

DataAccessLayer.m

#import "DataAccessLayer.h"
@interface DataAccessLayer ()
- (NSURL *)applicationDocumentsDirectory;
@end

@implementation DataAccessLayer
@synthesize storeCoordinator;
@synthesize managedObjectModel;
@synthesize managedObjectContext;

+ (DataAccessLayer *)sharedInstance {
  __strong static DataAccessLayer *sharedInstance = nil;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    sharedInstance = [[DataAccessLayer alloc] init];
    sharedInstance.storeCoordinator = [sharedInstance persistentStoreCoordinator];
    sharedInstance.managedObjectContext = [sharedInstance managedObjectContext];
  });
  return sharedInstance;
}

#pragma mark - Core Data

- (void)saveContext {
  @synchronized(self) {
    NSError *error = nil;
    if (managedObjectContext != nil)
    {
      if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error])
      {
        NSLog(@"error: %@", error.userInfo);
        /*
         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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Oops!"
                                                        message:@"Something has gone terribly wrong! You need to reinstall the app in order for it to work properly."
                                                       delegate:nil
                                              cancelButtonTitle:@"Close."
                                              otherButtonTitles:nil, nil];
        [alert show];
      } 
    }
  }
}

#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;
  }

  if (storeCoordinator != nil)
  {
    managedObjectContext = [[NSManagedObjectContext alloc] init];
    [managedObjectContext setPersistentStoreCoordinator:storeCoordinator];
  }
  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:@"DataModel" 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 (storeCoordinator != nil)
  {
    return storeCoordinator;
  }

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

  NSError *error = nil;
  storeCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
  if (![storeCoordinator 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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.

     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]);
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Oops!"
                                                    message:@"Something has gone terribly wrong! You need to reinstall the app in order for it to work properly."
                                                   delegate:nil
                                          cancelButtonTitle:@"Close."
                                          otherButtonTitles:nil, nil];
    [alert show];
  }    

  return storeCoordinator;
}

#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

您还必须创建.xcdatamodeld文件才能创建数据模型对象。并使用适当的

替换此处的名称

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

没有主要详细模板的核心数据

1 个答案: