IOS学习笔记（八）CoreData

RootViewController.h

@interface RootViewController : UITableViewController<NSFetchedResultsControllerDelegate>
{
    NSManagedObjectContext *managedObjectContext;//被管理对象上下文
    //使用Core Data的框架，大多数的功能都可以自动实现，因为我们有managed object context（管理对象的上下文，有时直接叫"Context"）。managed object context就像是一个关卡，通过它可以访问框架底层的对象——这些对象的集合我们称之为"persistence stack"（数据持久栈）。 managed object context作为程序中对象和外部的数据存储的中转站。栈的底部是persistence object stores（持久化数据存储）
    NSFetchedResultsController *__fetchedResultsController;//fetchedResultsController
    //NSFetchedResultsController和UITableView集成起来处理数据具有强大的灵活性。一般来说，你会创建一个NSFetchedResultsController实例作为table view的成员变量。
    //我们知道表格视图有很多种形式, fetched results 控制器主要针对列表视图，这种视图是由很多section组成的，每个section又包含了很多row。我们只需要在使用时配置 NSFetchedResultsController对象：entity是什么，如何排序（必须配置），预筛选项（可选）。NSFetchedResultsController就会自动帮你处理好每个section都应该显示哪些数据。
    
    
    UISearchBar *searchBar;//搜索
    //NSFetchedResultsController *__search_fetchedResultsController;
    NSMutableArray *searchResultArray;
}

@property(nonatomic,strong)NSManagedObjectContext *managedObjectContext;
@property(nonatomic,strong)NSFetchedResultsController *fetchedResultsController;
//@property(nonatomic,strong)NSFetchedResultsController *search_fetchedResultsController;
@end

RootViewController.m

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
        id delegate = [[UIApplication sharedApplication] delegate];//设置代理为AppDelegate
        //在初始化函数中，我们看到通过获取delegate，再通过delegate调用方法managedObjectContext，这样就得到了这个NSManagedObjectContext对象，NSManagedObjectContext对象它会跟NSPersistentStoreCoordinator对象打交道，NSPersistentStoreCoordinator会去处理底层的存储方式。
        self.managedObjectContext = [delegate managedObjectContext];//得到被管理对象上下文
        
//        NSString *path = [[NSBundle mainBundle]pathForResource:@"backg" ofType:@"jpg"];
//        UIImage *backgroudImage =[UIImage imageWithContentsOfFile:path];
//        [self.view setBackgroundColor:[UIColor colorWithPatternImage:backgroudImage]];

    }
    return self;
}

-(void)addButtonPushed:(UIBarButtonItem *)button
{
    AddStudentViewController *addStudentViewController = [[AddStudentViewController alloc]init];
    //从底部push view
    CATransition *animation = [CATransition animation];
    [animation setType:kCATransitionMoveIn];
    [animation setSubtype:kCATransitionFromTop];
    [animation setDuration:1.0f];
    [animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault]];
    [self.navigationController pushViewController:addStudentViewController animated:NO];
    [self.navigationController.view.layer addAnimation:animation forKey:@"pushView"];
    [addStudentViewController release];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if(tableView == self.tableView)
    {
        id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections]objectAtIndex:section];
        //This protocol defines the interface for section objects vended by an instance of NSFetchedResultsController.
        //这个协议定义了由NSFetchedResultsController返回的section对象的接口
        return [sectionInfo numberOfObjects];//返回section对象中的对象数量
    }
}

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {//删除操作
        // Delete the row from the data source
        NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
        [context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
        //通过fetchedResultsController在上下文中删除indexpath处的对象
        NSError *error;
        if(![context save:&error])
        {
            NSLog(@"Unresolved error %@, %@",error,[error userInfo]);
            abort();
        }
    }   

    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }   
}

#pragma mark - NSFetchedResultsControllerDelegate
//NSFetchedResultsController代理方法 通常都用如下格式
//如果你为fetched results控制器设置了代理，代理会收到从它的managed object context中传来改变通知。delegate会处理context中任何会影响结果集或者section的变化，results也做相应的更新。控制器会告诉delegate结果集改变了什么或者section变化了哪些。你只要覆写几个方法来更新table view就行。

-(void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
    [self.tableView beginUpdates];//在controllerWillChangeContent:方法中指定开始更新
}
-(void)controller:(NSFetchedResultsController *)controller didChangeSection:(id<NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type//更新section的方法
{
    switch (type) {
        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];//插入section
            break;
        case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];//删除section
            break;
        default:
            break;
    }
}
-(void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath//更新row的方法
{
    //    enum {
    //        NSFetchedResultsChangeInsert = 1,
    //        NSFetchedResultsChangeDelete = 2,
    //        NSFetchedResultsChangeMove = 3,
    //        NSFetchedResultsChangeUpdate = 4
    //    };NSFetchedResultsChangeType
    UITableView *tableView = self.tableView;
    switch (type) {
        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];//在newIndexPath处插入行
            break;
        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];//在indexPath处删除行
            break;
        case NSFetchedResultsChangeUpdate:
            [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];//更新行
            break;
        case NSFetchedResultsChangeMove://移动行
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];//先删除旧的indexPath处的行
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];//再插入到newIndexPath处
            break;
        default:
            break;
    }
}
-(void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    [self.tableView endUpdates];//在controllerDidChangeContent:方法中指定结束更新
}

-(void)addStudent//利用被管理对象上下文添加学生
{
    if([self.nameTextField.text length] == 0)
    {
        NSLog(@"here");
        UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"错误" message:@"姓名不能为空" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];
        [alert show];
        return;
    }

    Student *student = [NSEntityDescription insertNewObjectForEntityForName:@"Student" inManagedObjectContext:self.managedObjectContext];//创建新的学生对象
    student.name = self.nameTextField.text;//学生姓名
    student.age = [[NSNumber alloc]initWithInt:[self.ageTextField.text intValue]];//学生年龄
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
    [dateFormatter setDateFormat:@"yyyy-MM-dd"];
    student.birthday = [dateFormatter dateFromString:self.birthdayTextField.text];//学生出生年月
    
    //照片 在document中生成一张png图片，把路径跑村在student.image中
    if(currentImage != nil)
    {
        NSData *imageData = UIImagePNGRepresentation(currentImage);
        NSString *homePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)objectAtIndex:0];
        NSLog(@"homepath = %@",homePath);
        NSString *fileName = [NSString stringWithFormat:@"%@%d",student.name,[student.age intValue]];
        NSFileManager *fileManager = [NSFileManager defaultManager];
        
        NSString *path = [homePath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",fileName]];
        if([fileManager fileExistsAtPath:path])
        {
            fileName  = [fileName stringByAppendingFormat:@"1"];
            path = [homePath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",fileName]];
        }
        NSLog(@"path = %@",path);
        NSError *err = nil;
        [imageData writeToFile:path options:NSDataWritingAtomic error:&err];
        if(err)
        {
            NSLog(@"error = %@",[err description]);
        }
        student.image = [NSString stringWithFormat:@"%@.png",fileName];
    }
    
    //student.photo = [NSString stringWithFormat:@"%d",arc4random()%25];
    NSError *error = nil;
    if(![managedObjectContext save:&error])//把上下文中的操作保存到持久库中
    {
        NSLog(@"Unresolved error %@, %@",error,[error userInfo]);
        abort();
    }
    [self.navigationController popViewControllerAnimated:YES];//从navigationController中出栈
}