关于Core Data的一些整理（一）

在Xcode7.2中只有Mast-Debug和Single View中可以勾选Use Core Data

如果勾选了Use Core Data，Xcode会自动在AppDelegate中帮你生成Core Data的核心代码，并且自动生成.xcdatamodeld数据文件

 //Appdelegate.h中

 #import <UIKit/UIKit.h>

 #import <CoreData/CoreData.h>

 @interface AppDelegate : UIResponder <UIApplicationDelegate>

 @property (strong, nonatomic) UIWindow *window;

 @property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;

 @property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;

 @property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;

 - (void)saveContext;

 - (NSURL *)applicationDocumentsDirectory;

 @end

 //Appdelegate.m中系统帮助生成的代码

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

   // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.

   // Saves changes in the application's managed object context before the application terminates.

   [self saveContext];

 }

 #pragma mark - Core Data stack

 @synthesize managedObjectContext = _managedObjectContext;

 @synthesize managedObjectModel = _managedObjectModel;

 @synthesize persistentStoreCoordinator = _persistentStoreCoordinator;

 - (NSURL *)applicationDocumentsDirectory {

     // The directory the application uses to store the Core Data store file. This code uses a directory named "qq100858433.JMHitList" in the application's documents directory.

     return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];

 }

 - (NSManagedObjectModel *)managedObjectModel {

     // The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.

     if (_managedObjectModel != nil) {

         return _managedObjectModel;

     }

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

     _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];

     return _managedObjectModel;

 }

 - (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

     // The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added the store for the application to it.

     if (_persistentStoreCoordinator != nil) {

         return _persistentStoreCoordinator;

     }

     // Create the coordinator and store

     _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

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

     NSError *error = nil;

     NSString *failureReason = @"There was an error creating or loading the application's saved data.";

     if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {

         // Report any error we got.

         NSMutableDictionary *dict = [NSMutableDictionary dictionary];

         dict[NSLocalizedDescriptionKey] = @"Failed to initialize the application's saved data";

         dict[NSLocalizedFailureReasonErrorKey] = failureReason;

         dict[NSUnderlyingErrorKey] = error;

         error = [NSError errorWithDomain:@"YOUR_ERROR_DOMAIN" code: userInfo:dict];

         // Replace this 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();

     }

     return _persistentStoreCoordinator;

 }

 - (NSManagedObjectContext *)managedObjectContext {

     // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)

     if (_managedObjectContext != nil) {

         return _managedObjectContext;

     }

     NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];

     if (!coordinator) {

         return nil;

     }

     _managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];

     [_managedObjectContext setPersistentStoreCoordinator:coordinator];

     return _managedObjectContext;

 }

 #pragma mark - Core Data Saving support

 - (void)saveContext {

     NSManagedObjectContext *managedObjectContext = self.managedObjectContext;

     if (managedObjectContext != nil) {

         NSError *error = 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();

         }

     }

 }

 @end

假如你在.xcdatamodeld中生成了如下实体和实体属性：

那么在VC中获取数据库内容和添加数据库内容的代码如下：

   //从Core Data中获得已有数据

   id appDelegate = [UIApplication sharedApplication].delegate;

   NSManagedObjectContext *managedContext = [appDelegate managedObjectContext];

   NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Person"];

   @try {

     self.people = [NSMutableArray arrayWithArray:[managedContext executeFetchRequest:fetchRequest error:nil]];

   }

   @catch (NSException *exception) {

     NSLog(@"Could not fetch %@", [exception userInfo]);

   }

   @finally {

     NSLog(@"Fetch Successful");

   }

   //为数据库添加实体实例

   id appDelegate = [UIApplication sharedApplication].delegate;

   //NSManagedObjectContext可以看做内存中用来处理managedObjects的暂存器

   NSManagedObjectContext *mangedContext = [appDelegate managedObjectContext];

   //下面两种方法都可以获得Person实体

 //  NSEntityDescription *entity = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:mangedContext];

 //  NSManagedObject *person = [[NSManagedObject alloc] initWithEntity:entity insertIntoManagedObjectContext:mangedContext];

 //  [person setValue:name forKey:@"name"];

   NSManagedObject *person = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:mangedContext];

   [person setValue:name forKey:@"name"];

   @try {

     [mangedContext save:nil];

     [self.people addObject:person];

   }

   @catch (NSException *exception) {

     NSLog(@"Could not save %@", [exception userInfo]);

   }

   @finally {

     NSLog(@"Save Successfullt!");

   }

巴特西

关于Core Data的一些整理（一）

关于Core Data的一些整理（一）

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