IOS学习笔记（八）CoreData

RootViewController.h

 1 @interface RootViewController : UITableViewController<NSFetchedResultsControllerDelegate>
 2 {
 3     NSManagedObjectContext *managedObjectContext;//被管理对象上下文
 4     //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）
 5     NSFetchedResultsController *__fetchedResultsController;//fetchedResultsController
 6     //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。
 7     //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。
 8     
 9     
10     UISearchBar *searchBar;//搜索
11     //NSFetchedResultsController *__search_fetchedResultsController;
12     NSMutableArray *searchResultArray;
13 }
14 
15 @property(nonatomic,strong)NSManagedObjectContext *managedObjectContext;
16 @property(nonatomic,strong)NSFetchedResultsController *fetchedResultsController;
17 //@property(nonatomic,strong)NSFetchedResultsController *search_fetchedResultsController;
18 @end

RootViewController.m

 1 - (id)initWithStyle:(UITableViewStyle)style
 2 {
 3     self = [super initWithStyle:style];
 4     if (self) {
 5         // Custom initialization
 6         id delegate = [[UIApplication sharedApplication] delegate];//设置代理为AppDelegate
 7         //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。
 8         self.managedObjectContext = [delegate managedObjectContext];//得到被管理对象上下文
 9         
10 //        NSString *path = [[NSBundle mainBundle]pathForResource:@"backg" ofType:@"jpg"];
11 //        UIImage *backgroudImage =[UIImage imageWithContentsOfFile:path];
12 //        [self.view setBackgroundColor:[UIColor colorWithPatternImage:backgroudImage]];
13 
14     }
15     return self;
16 }

-(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
    }
}

 1 - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
 2 {
 3     if (editingStyle == UITableViewCellEditingStyleDelete) {//删除操作
 4         // Delete the row from the data source
 5         NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
 6         [context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
 7         //通过fetchedResultsController在上下文中删除indexpath处的对象
 8         NSError *error;
 9         if(![context save:&error])
10         {
11             NSLog(@"Unresolved error %@, %@",error,[error userInfo]);
12             abort();
13         }
14     }   
15 
16     else if (editingStyle == UITableViewCellEditingStyleInsert) {
17         // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
18     }   
19 }

 1 #pragma mark - NSFetchedResultsControllerDelegate
 2 //NSFetchedResultsController代理方法 通常都用如下格式
 3 //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。
 4 
 5 -(void)controllerWillChangeContent:(NSFetchedResultsController *)controller
 6 {
 7     [self.tableView beginUpdates];//在controllerWillChangeContent:方法中指定开始更新
 8 }
 9 -(void)controller:(NSFetchedResultsController *)controller didChangeSection:(id<NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type//更新section的方法
10 {
11     switch (type) {
12         case NSFetchedResultsChangeInsert:
13             [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];//插入section
14             break;
15         case NSFetchedResultsChangeDelete:
16             [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];//删除section
17             break;
18         default:
19             break;
20     }
21 }
22 -(void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath//更新row的方法
23 {
24     //    enum {
25     //        NSFetchedResultsChangeInsert = 1,
26     //        NSFetchedResultsChangeDelete = 2,
27     //        NSFetchedResultsChangeMove = 3,
28     //        NSFetchedResultsChangeUpdate = 4
29     //    };NSFetchedResultsChangeType
30     UITableView *tableView = self.tableView;
31     switch (type) {
32         case NSFetchedResultsChangeInsert:
33             [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];//在newIndexPath处插入行
34             break;
35         case NSFetchedResultsChangeDelete:
36             [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];//在indexPath处删除行
37             break;
38         case NSFetchedResultsChangeUpdate:
39             [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];//更新行
40             break;
41         case NSFetchedResultsChangeMove://移动行
42             [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];//先删除旧的indexPath处的行
43             [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];//再插入到newIndexPath处
44             break;
45         default:
46             break;
47     }
48 }
49 -(void)controllerDidChangeContent:(NSFetchedResultsController *)controller
50 {
51     [self.tableView endUpdates];//在controllerDidChangeContent:方法中指定结束更新
52 }

 1 -(void)addStudent//利用被管理对象上下文添加学生
 2 {
 3     if([self.nameTextField.text length] == 0)
 4     {
 5         NSLog(@"here");
 6         UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"错误" message:@"姓名不能为空" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];
 7         [alert show];
 8         return;
 9     }
10 
11     Student *student = [NSEntityDescription insertNewObjectForEntityForName:@"Student" inManagedObjectContext:self.managedObjectContext];//创建新的学生对象
12     student.name = self.nameTextField.text;//学生姓名
13     student.age = [[NSNumber alloc]initWithInt:[self.ageTextField.text intValue]];//学生年龄
14     NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
15     [dateFormatter setDateFormat:@"yyyy-MM-dd"];
16     student.birthday = [dateFormatter dateFromString:self.birthdayTextField.text];//学生出生年月
17     
18     //照片 在document中生成一张png图片，把路径跑村在student.image中
19     if(currentImage != nil)
20     {
21         NSData *imageData = UIImagePNGRepresentation(currentImage);
22         NSString *homePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)objectAtIndex:0];
23         NSLog(@"homepath = %@",homePath);
24         NSString *fileName = [NSString stringWithFormat:@"%@%d",student.name,[student.age intValue]];
25         NSFileManager *fileManager = [NSFileManager defaultManager];
26         
27         NSString *path = [homePath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",fileName]];
28         if([fileManager fileExistsAtPath:path])
29         {
30             fileName  = [fileName stringByAppendingFormat:@"1"];
31             path = [homePath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",fileName]];
32         }
33         NSLog(@"path = %@",path);
34         NSError *err = nil;
35         [imageData writeToFile:path options:NSDataWritingAtomic error:&err];
36         if(err)
37         {
38             NSLog(@"error = %@",[err description]);
39         }
40         student.image = [NSString stringWithFormat:@"%@.png",fileName];
41     }
42     
43     //student.photo = [NSString stringWithFormat:@"%d",arc4random()%25];
44     NSError *error = nil;
45     if(![managedObjectContext save:&error])//把上下文中的操作保存到持久库中
46     {
47         NSLog(@"Unresolved error %@, %@",error,[error userInfo]);
48         abort();
49     }
50     [self.navigationController popViewControllerAnimated:YES];//从navigationController中出栈
51 }