iOS数据持久化（三）

#pragma mark - Core Data stack
/**
 *  @synthesize 关联成员变量和属性
 */
@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 "CD._8_25_CoreData" 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;
    }
    //找到momd文件在bundle中的途径。
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"_8_25_CoreData" withExtension:@"momd"];
    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return _managedObjectModel;
}
//重写get
- (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
    //创建数据存储器的文件路径
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"_8_25_CoreData.sqlite"];
    NSError *error = nil;
    NSString *failureReason = @"There was an error creating or loading the application's saved data.";
    //coreData 不是对sqlite的封装，sqlite 只是其中一种存储方式
    //coredata的核心思想是：托管对象
    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:9999 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]);
        //终止程序
        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;
    }
    //设置上下文
    _managedObjectContext = [[NSManagedObjectContext alloc] init];
    [_managedObjectContext setPersistentStoreCoordinator:coordinator];
    return _managedObjectContext;
}

#pragma mark - Core Data Saving support

- (void)saveContext {
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil) {
        NSError *error = nil;
         //如果上下文有修改，并且保存失败
        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();
        }
    }
}

　　

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
//    [self.tableView registerClass:[ UITableViewCell class] forCellReuseIdentifier:@"cell"];
    self.dataArray = [NSMutableArray arrayWithCapacity:0];
    AppDelegate *delegate = [UIApplication sharedApplication].delegate;
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
    //在上下文内通过条件获取响应数据
    NSArray *array = [delegate.managedObjectContext executeFetchRequest:request error:nil];
    [self.dataArray addObjectsFromArray:array];
    [self.tableView reloadData];
}

　　

- (IBAction)addPerson:(UIButton *)sender {
    AppDelegate *delegate = [UIApplication sharedApplication].delegate;
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:delegate.managedObjectContext];
    Person *per = [[Person alloc] initWithEntity:entity insertIntoManagedObjectContext:delegate.managedObjectContext];
    per.age = @(arc4random()%20 + 10);
    NSArray *array = @[@"萌萌",@"波波",@"jack",@"rose",@"静静",@"000"];
    per.name = array[arc4random() % (array.count)];
    
    [self.dataArray addObject:per];
    [self.tableView insertRowsAtIndexPaths:@[[NSIndexPath indexPathForRow:self.dataArray.count - 1 inSection:0]] withRowAnimation:UITableViewRowAnimationMiddle];
    
    [self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:self.dataArray.count - 1 inSection:0] atScrollPosition:UITableViewScrollPositionBottom animated:YES];
}

　　

- (IBAction)searchPerson:(UIButton *)sender {
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
    request.predicate = [NSPredicate predicateWithFormat:@"age>18"];

    AppDelegate *delegate = [UIApplication sharedApplication].delegate;
    NSArray *array = [delegate.managedObjectContext executeFetchRequest:request error:nil];
    
    [self.dataArray removeAllObjects];
    [self.dataArray addObjectsFromArray:array];
}

　　

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        AppDelegate *delegate = [UIApplication sharedApplication].delegate;
        [delegate.managedObjectContext deleteObject:self.dataArray[indexPath.row]];
        [self.dataArray removeObjectAtIndex:indexPath.row];
        [tableView  deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationMiddle];
    }
}