NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);

 NSString *dd = [paths objectAtIndex:];

 NSString *tempPath = NSTemporaryDirectory();

 NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

 //使用属性列表保存3个用户的账号密码

     accountList = [[NSMutableArray alloc] init];

     [accountList addObject:[NSDictionary

                                 dictionaryWithObjects:[NSArray arrayWithObjects:@"loginname",@"loginpwd", nil]

                                 forKeys:[NSArray arrayWithObjects:@"",@"", nil]]];

     [accountList addObject:[NSDictionary

                             dictionaryWithObjects:[NSArray arrayWithObjects:@"loginname",@"loginpwd", nil]

                             forKeys:[NSArray arrayWithObjects:@"",@"", nil]]];

     [accountList addObject:[NSDictionary

                             dictionaryWithObjects:[NSArray arrayWithObjects:@"loginname",@"loginpwd", nil]

                             forKeys:[NSArray arrayWithObjects:@"",@"", nil]]];

     [accountList writeToFile:[self filePath] atomically:YES];

     //使用UIActionSheet提示用户保存成功

     UIActionSheet *sheet =[[UIActionSheet alloc] initWithTitle:@"保存成功" delegate:nil cancelButtonTitle:nil destructiveButtonTitle:@"确定" otherButtonTitles:nil, nil];

     [sheet showInView:self.view];

 #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 "esitech.Unit_3" 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;

     }

     //获取实体模型文件对应的nsurl

     NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Unit_3" withExtension:@"momd"];

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

     return _managedObjectModel;

 }

 - (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

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

     if (_persistentStoreCoordinator != nil) {

         return _persistentStoreCoordinator;

     }

     // Create the coordinator and store

     //以持久化模型为基础，创建持久化存储协调器对象

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

     //获取sqlite数据库文件的存储目录

     NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Unit_3.sqlite"];

     NSError *error = nil;

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

     //设置存储协调器采用sqlite，如果失败打印失败信息

     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] init];

     //设置上下文使用的持久化类型

     [_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();

         }

     }

 }

 //删除操作

 - (IBAction)btnRemove_Tap:(id)sender {

     //获取要删除的实体

     EventEntity *entity = [self getEntityByName:@"名字1"];

     //从上下文对象中删除该实体

     [self.appDelete.managedObjectContext deleteObject:entity];

     NSError *error;

     if (![self.appDelete.managedObjectContext save:&error]) {

         NSLog(@"删除时出现错误：%@,%@",error,[error userInfo]);

     }

 }

5.3 修改实体

 //更新操作

 - (IBAction)btnUpdate_Tap:(id)sender {

     //获取要删除的实体

     EventEntity *entity = [self getEntityByName:@"名字1"];

     //修改实体属性

     entity.happenDate = [NSDate date];

     NSError *error;

     if (![self.appDelete.managedObjectContext save:&error]) {

         NSLog(@"删除时出现错误：%@,%@",error,[error userInfo]);

     }

 }

5.4 查询

 //根据名字查询一个对象

 -(EventEntity *)getEntityByName:(NSString *) name

 {

     //创建抓取数据的请求对象

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

     //设置要抓取哪种类型的实体

     NSEntityDescription *des = [NSEntityDescription entityForName:@"EventEntity" inManagedObjectContext:self.appDelete.managedObjectContext];

     //设置抓取实体

     [request setEntity:des];

     //定义抓取条件

     NSPredicate * qcmd = [NSPredicate predicateWithFormat:@"name = %@ ",name];

     [request setPredicate:qcmd];

     NSError *error = nil;

     //执行查询请求

     NSArray *result = [[self.appDelete.managedObjectContext executeFetchRequest:request error:&error] copy];

     if (error!=nil) {

         NSLog(@"查询单个时出现错误：%@,%@",error,[error userInfo]);

         return nil;

     }

     if (result.count==) {

         return nil;

     }

     return result[];

 }

 //获得所有实体

 -(NSArray *)getAllEntities

 {

     //创建抓取数据的请求对象

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

     //设置要抓取哪种类型的实体

     NSEntityDescription *des = [NSEntityDescription entityForName:@"EventEntity" inManagedObjectContext:self.appDelete.managedObjectContext];

     //设置抓取实体

     [request setEntity:des];

     NSError *error = nil;

     //执行查询请求

     NSArray *result = [[self.appDelete.managedObjectContext executeFetchRequest:request error:&error] copy];

     //如果没有数据返回nil

     if (error!=nil && result == ) {

         return nil;

     }

     return result;

 }