在删除coredata中的对象后，按照通知重新加载tableview显示奇怪的结果
我是新来的这个coredata。 只是为了熟悉关系，我创build了两个实体CategoryList（由属性'categories'组成）和ExpenseList（由属性'rangespent'组成），它们具有多种关系。 从'CategoryList'到'ExpenseList'的关系是'expenseselist'。 第一个tableview显示每个类别的总费用
food -150 transportation -100 mobile -100 shopping -500 而第二个tableview显示的是个人开支
food -100 food -50 transportation -100 mobile -50 mobile -50 shopping -200 shopping -100 shopping -200
我已经写了代码，从我的第二个tableview中删除一个单独的费用行使用对象ID，因为它的线程安全。 当我从我的第二个表格视图删除食物条目说
food -50
当我回到第一个tableview时，它应该更新食物和显示
food -100
我已经注册了第一个默认通知中心的tableview，第一个表视图发送通知（通过nslog检查）每当一个对象被删除。 当第一个tableview接收到一个通知它重新加载tableview中的数据。 但是，当重新加载tableview显示的对象被从下一个tableview中删除的类别意想不到的价值。 这两个tableviews通过导航控制器连接。
这是我的第一个tableview的m.file。
#import "displayTable.h" #import "CategoryList.h" #import "ExpenseList.h" #import "IncomeList.h" #import "coreAppDelegate.h" @interface displayTable () @end @implementation displayTable - (NSManagedObjectContext *)managedObjectContext { NSManagedObjectContext *context = nil; id delegate = [[UIApplication sharedApplication] delegate]; if ([delegate performSelector:@selector(managedObjectContext)]) { context = [delegate managedObjectContext]; } return context; } - (id)initWithStyle:(UITableViewStyle)style { self = [super initWithStyle:style]; if (self) { // Custom initialization } return self; } - (void)viewDidLoad { [super viewDidLoad]; todaysL = [[todayslist alloc]init]; self.expenseArray = [[NSMutableArray alloc] initWithObjects:@"0.00", @"0.00", @"0.00", @"0.00", @"0.00", @"0.00", nil]; self.categoryArray = [[NSMutableArray alloc] initWithObjects:@"food", @"transportation", @"fuel", @"mobile", @"shopping", @"others", nil]; [self populateExpenses]; NSOperationQueue *mainQueue = [NSOperationQueue mainQueue]; [[NSNotificationCenter defaultCenter] addObserverForName:NSManagedObjectContextObjectsDidChangeNotification object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification *notification) { NSLog(@"Notification received!"); [self populateExpenses]; // [self viewDidLoad]; [self.tableView reloadData]; }]; // Uncomment the following line to preserve selection between presentations. // self.clearsSelectionOnViewWillAppear = NO; // Uncomment the following line to display an Edit button in the navigation bar for this view controller. // self.navigationItem.rightBarButtonItem = self.editButtonItem; } - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } #pragma mark-Table view data source - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { //#warning Potentially incomplete method implementation. // Return the number of sections. return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { //#warning Incomplete method implementation. // Return the number of rows in the section. return [self.categoryArray count]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath]; // Configure the cell... if(cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier]; } cell.textLabel.text = [_categoryArray objectAtIndex:indexPath.row]; cell.detailTextLabel.text = [_expenseArray objectAtIndex:indexPath.row]; return cell; }
这是我获取数据的函数
-(void)populateExpenses { NSManagedObjectContext *managedObjectContexts = [self managedObjectContext]; NSEntityDescription *categorylistEntity = [NSEntityDescription entityForName:@"CategoryList" inManagedObjectContext:managedObjectContext]; NSFetchRequest *request = [[NSFetchRequest alloc]init]; [request setEntity:categorylistEntity]; NSError *error =nil; NSArray *fetchedObjects = [managedObjectContext executeFetchRequest:request error:&error]; if(fetchedObjects == nil) { NSLog(@"your fetching cause error"); } else { for(CategoryList *categoryL in fetchedObjects) { if([categoryL.categories isEqualToString: @"food"] ) { for(ExpenseList *expenseL in categoryL.expenselist) { food = food + expenseL.amountSpent; //NSLog(@"display food %f",food); } NSString *foodString = [NSString stringWithFormat:@"%.2f",food]; [self.expenseArray replaceObjectAtIndex:0 withObject:foodString]; //NSLog(@"foooood%f",food); } else if ([categoryL.categories isEqualToString: @"transportation"]) { for(ExpenseList *expenseL in categoryL.expenselist) { transportation = transportation + expenseL.amountSpent; } NSString *transportationString = [NSString stringWithFormat:@"%.2f",transportation]; [self.expenseArray replaceObjectAtIndex:1 withObject:transportationString]; } else if ([categoryL.categories isEqualToString: @"fuel"]) { for(ExpenseList *expenseL in categoryL.expenselist) { fuel = fuel + expenseL.amountSpent; } NSString *fuelString = [NSString stringWithFormat:@"%.2f",fuel]; [self.expenseArray replaceObjectAtIndex:2 withObject:fuelString]; } else if([categoryL.categories isEqualToString: @"mobile"]) { for(ExpenseList *expenseL in categoryL.expenselist) { mobile = mobile + expenseL.amountSpent; } NSString *mobileString = [NSString stringWithFormat:@"%.2f",mobile]; [self.expenseArray replaceObjectAtIndex:3 withObject:mobileString]; } else if([categoryL.categories isEqualToString: @"shopping"]) { for(ExpenseList *expenseL in categoryL.expenselist) { shopping = shopping + expenseL.amountSpent; } NSString *shoppingString = [NSString stringWithFormat:@"%.2f",shopping]; [self.expenseArray replaceObjectAtIndex:4 withObject:shoppingString]; } else if ([categoryL.categories isEqualToString:@"others"]) for(ExpenseList *expenseL in categoryL.expenselist) { others = others + expenseL.amountSpent; } NSString *othersString = [NSString stringWithFormat:@"%.2f",others]; [self.expenseArray replaceObjectAtIndex:5 withObject:othersString]; NSLog(@"%@",othersString); } //NSLog(@"count %d", self.expenseArray.count); } } /* // Override to support conditional editing of the table view. - (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath { // Return NO if you do not want the specified item to be editable. return YES; } */ /* // Override to support editing the table view. - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the row from the data source [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade]; } 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 } } */ /* // Override to support rearranging the table view. - (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath { } */ /* // Override to support conditional rearranging of the table view. - (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath { // Return NO if you do not want the item to be re-orderable. return YES; } */ #pragma mark - Table view delegate - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { // Navigation logic may go here. Create and push another view controller. /* <#DetailViewController#> *detailViewController = [[<#DetailViewController#> alloc] initWithNibName:@"<#Nib name#>" bundle:nil]; // ... // Pass the selected object to the new view controller. [self.navigationController pushViewController:detailViewController animated:YES]; */ } @end
但是当我退出并重新启动我的应用程序时，所有更新，因为它应该是，但不删除后立即更新。 我不明白为什么。 我也不知道这是否是正确的做法与coredata的方式。 如果有人能指导我，请提前致谢
是的，你错过了核心数据的一些核心概念，这意味着你正在做的工作比你需要的多得多。
您有数据库中顶级类别的名称，但是您不知道按照什么顺序进入，所以您创build一个单独的数组，然后执行一些复杂的工作以从数据库中获取值以相同的顺序。 更好的方法是在数据库中添加一个“displayOrder”字段，然后在字段中添加一个order to the fetch。
完全摆脱你的categoryArray属性，并在你的populateExpenses函数，只要执行提取（使用sorting子句）。 将fetchedObjects保存到数组属性。
你需要做一个抓取来获得你的顶级对象，但是一旦你拥有了它们，你很less需要做更多的抓取。
在你的cellForRowAtIndexPath中：
CategoryList * category = [_fetchedObjects objecatAtIndex：indexPath.row]; cell.textLabel.text = category.categories; cell.detailTextLabel.text = [[category valueForKeyPath：@“expenseselist。@ sum.amountSpent”] description];
您不需要预取，您可以在显示数据时进行此操作。
更新对象以确保您的更改被注意到： –
for ( NSManagedObject* object in self.categoryArray) { [self.managedObjectContext refreshObject: object mergeChanges:YES]; }
这在大多数情况下会告诉对象下一次请求时需要重新更新它的值。
希望这可以帮助。
我把它存储在数组后，只清除浮点型variables值就解决了。 因为我之前没有清理浮点variables，而在重新加载表视图时，浮点variables中的以前的值也会再次被添加，从而给出不希望的值。 所以在viewWillAppear方法我写了重新加载表视图和清除浮动variables的内容，它的工作。