当我删除核心数据实体的最后一条记录时，为啥我的应用程序崩溃了？
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【中文标题】当我删除核心数据实体的最后一条记录时，为啥我的应用程序崩溃了？【英文标题】：Why do my app crashed when I delete the last record of a core data entity?当我删除核心数据实体的最后一条记录时，为什么我的应用程序崩溃了？ 【发布时间】：2013-11-29 16:59:55 【问题描述】：在我的应用程序中，我使用表格视图中显示的两个核心数据实体，如果有多个记录，我可以毫无问题地删除它，但如果只有一条记录，触摸删除按钮后应用程序崩溃：
如果需要检测问题，这是我的代码，提前致谢：
#import "PersonsTVC.h"
#import "Person.h"
@implementation PersonsTVC
@synthesize fetchedResultsController = __fetchedResultsController;
@synthesize managedObjectContext = __managedObjectContext;
@synthesize selectedPerson;
@synthesize searchResults,titulosseccion;
- (void)setupFetchedResultsController
// 1 - Decide what Entity you want
NSString *entityName = @"Person"; // Put your entity name here
NSLog(@"Setting up a Fetched Results Controller for the Entity named %@", entityName);
// 2 - Request that Entity
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:entityName];
// 3 - Filter it if you want
//request.predicate = [NSPredicate predicateWithFormat:@"Person.name = Blah"];
// 4 - Sort it if you want
// First sort descriptor (required for grouping into sections):
NSSortDescriptor *sortByDate = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:NO];
// Second sort descriptor (for the items within each section):
NSSortDescriptor *sortByName = [[NSSortDescriptor alloc] initWithKey:@"firstname" ascending:YES];
[request setSortDescriptors:@[sortByDate, sortByName]];
//
// request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"firstname"
//ascending:YES
//selector:@selector(localizedCaseInsensitiveCompare:)]];
// 5 - Fetch it
self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:@"sectionIdentifier"
cacheName:nil];
[self performFetch];
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
id <NSFetchedResultsSectionInfo> theSection = [[self.fetchedResultsController sections] objectAtIndex:section];
NSString *sectionName = [theSection name];
if ([sectionName isEqualToString:@"0"])
return @"Today";
else if ([sectionName isEqualToString:@"1"])
return @"Tomorrow";
else if ([sectionName isEqualToString:@"2"])
return @"Upcoming";
return @"Other";
- (void) viewDidLoad
self.searchResults = [NSMutableArray arrayWithCapacity:[[self.fetchedResultsController fetchedObjects] count]];
[self.tableView reloadData];
- (void)viewWillAppear:(BOOL)animated
[super viewWillAppear:animated];
[self setupFetchedResultsController];
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
// Perform segue to detail when a SEARCH table cell is touched
if(tableView == self.searchDisplayController.searchResultsTableView)
[self performSegueWithIdentifier:@"Person Detail Segue" sender:tableView];
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
static NSString *CellIdentifier = @"Persons Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
// Configure the cell...
// Configure the cell...
Person *person = nil;
if (tableView == self.searchDisplayController.searchResultsTableView)
NSLog(@"Configuring cell to show search results");
person = [self.searchResults objectAtIndex:indexPath.row];
else
NSLog(@"Configuring cell to show normal data");
person = [self.fetchedResultsController objectAtIndexPath:indexPath];
NSString *fullname = [NSString stringWithFormat:@"%@ %@", person.firstname, person.surname];
cell.textLabel.text = person.firstname;
if ([person.inRole.color isEqual :@"Yellow"])
cell.imageView.image = [UIImage imageNamed:@"Yellow"];
if ([person.inRole.color isEqual :@"Black"])
cell.imageView.image = [UIImage imageNamed:@"Black"];
if ([person.inRole.color isEqual :@"Grey"])
cell.imageView.image = [UIImage imageNamed:@"Grey"];
if ([person.inRole.color isEqual :@"Red"])
cell.imageView.image = [UIImage imageNamed:@"Red"];
if ([person.inRole.color isEqual :@"Blue"])
cell.imageView.image = [UIImage imageNamed:@"Blue"];
if ([person.inRole.color isEqual :@"Dark Green"])
cell.imageView.image = [UIImage imageNamed:@"DarkGreen"];
if ([person.inRole.color isEqual :@"Light Green"])
cell.imageView.image = [UIImage imageNamed:@"LightGreen"];
if ([person.inRole.color isEqual :@"Light Blue"])
cell.imageView.image = [UIImage imageNamed:@"LightBlue"];
if ([person.inRole.color isEqual :@"Brown"])
cell.imageView.image = [UIImage imageNamed:@"Brown"];
if ([person.inRole.color isEqual :@"Dark Orange"])
cell.imageView.image = [UIImage imageNamed:@"DarkOrange"];
NSDate *fechasinformat = person.date;
NSString *fecha0 = [NSString stringWithFormat:@"%@", fechasinformat];
cell.detailTextLabel.text = fecha0;
return cell;
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
if (tableView == self.searchDisplayController.searchResultsTableView)
return [self.searchResults count];
else
return [[[self.fetchedResultsController sections] objectAtIndex:section] numberOfObjects];
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
if (editingStyle == UITableViewCellEditingStyleDelete)
[self.tableView beginUpdates]; // Avoid NSInternalInconsistencyException
// Delete the person object that was swiped
Person *personToDelete = [self.fetchedResultsController objectAtIndexPath:indexPath];
NSLog(@"Deleting (%@)", personToDelete.firstname);
[self.managedObjectContext deleteObject:personToDelete];
[self.managedObjectContext save:nil];
// Delete the (now empty) row on the table
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[self performFetch];
[self.tableView endUpdates];
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
if ([segue.identifier isEqualToString:@"Add Person Segue"])
NSLog(@"Setting PersonsTVC as a delegate of PersonDetailTVC");
PersonDetailTVC *personDetailTVC = segue.destinationViewController;
personDetailTVC.delegate = self;
NSLog(@"Creating a new person and passing it to PersonDetailTVC");
Person *newPerson = [NSEntityDescription insertNewObjectForEntityForName:@"Person"
inManagedObjectContext:self.managedObjectContext];
personDetailTVC.person = newPerson;
else if ([segue.identifier isEqualToString:@"Person Detail Segue"])
NSLog(@"Setting PersonsTVC as a delegate of PersonDetailTVC");
PersonDetailTVC *personDetailTVC = segue.destinationViewController;
personDetailTVC.delegate = self;
// Store selected Person in selectedPerson property
if(sender == self.searchDisplayController.searchResultsTableView)
NSIndexPath *indexPath = [self.searchDisplayController.searchResultsTableView indexPathForSelectedRow];
self.selectedPerson = [self.searchResults objectAtIndex:[indexPath row]];
else
NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
self.selectedPerson = [self.fetchedResultsController objectAtIndexPath:indexPath];
NSLog(@"Passing selected person (%@) to PersonDetailTVC", self.selectedPerson.firstname);
personDetailTVC.person = self.selectedPerson;
else
NSLog(@"Unidentified Segue Attempted!");
- (void)theSaveButtonOnThePersonDetailTVCWasTapped:(PersonDetailTVC *)controller
// do something here like refreshing the table or whatever
// close the delegated view
[controller.navigationController popViewControllerAnimated:YES];
#pragma mark -
#pragma mark Content Filtering
-(void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope
self.searchResults = [[self.fetchedResultsController fetchedObjects] filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings)
Person* person = evaluatedObject;
NSString* firstName = person.firstname;
//searchText having length < 3 should not be considered
if (!!searchText && [searchText length] < 3)
return YES;
if ([scope isEqualToString:@"All"] || [firstName isEqualToString:scope])
return ([firstName rangeOfString:searchText].location != NSNotFound);
return NO; //if nothing matches
]];
#pragma mark -
#pragma mark UISearchDisplayController Delegate Methods
- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString
[self filterContentForSearchText:searchString scope:@"All"];
return YES;
- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchScope:(NSInteger)searchOption
[self filterContentForSearchText:[self.searchDisplayController.searchBar text] scope:@"All"];
return YES;
@end
【问题讨论】：
你的 UIFetchedResultsController 委托方法在哪里？ @JAManfredi：我无法回答你的问题......我不知道你的意思...... 对不起，我的意思是 NSFetchedResultsController，但你得到的错误是什么？ 这个问题与核心数据无关，是另一个错误；那是错误日志：'无效更新：无效的部分数。更新后表视图中包含的节数（0）必须等于更新前表视图中包含的节数（1），加上或减去插入或删除的节数（0插入，0已删除）。' 【参考方案1】：看起来您从未通过 tableview 数据源方法设置表格中的部分数量，这应该注意这一点：
- (NSInteger) numberOfSectionsInTableView:(UITableView *)tableView
// Return the number of sections.
return [[self.fetchedResultsController sections] count];
如果这不能解决问题，我认为是由于您缺少 NSFetchedResultControllerDelegate 方法（至少是 controllerDidChangeContent :)，这是我几天前回答的另一个问题：update CoreData Object not working correct
看看我的回答和对应的代码，希望对你有帮助！
【讨论】：
感谢@JAManfredi，但这不是解决方案，因为应用程序崩溃再次显示相同的错误。 查看我的编辑，几天前我回答了类似的问题，如果有帮助请告诉我 您必须设置您的 fetchedResultsController 委托，然后查看下面的代码#pragma mark - NSFetchedResultsController Delegate
对不起@JAManfredi，我不是一个经验丰富的开发人员，我不知道该怎么做，我已经把 -(void)controllerWillChangeContent:(NSFetchedResultsController *)controller [self.tableView beginUpdates] ; 在我的#pragma 标记部分下方，但再次崩溃，您能否更清楚地告诉我，我必须将哪些代码行添加到我的代码中才能解决问题？所以我会明白错误在哪里。先感谢您。我不确切知道如何实现委托..【参考方案2】：
一个部分不能为空，因此当您删除最后一行时，您也需要删除该部分（并且不要忘记在添加第一个对象之前创建它）：
// Delete the (now empty) row on the table
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
// Delete the section if needed
if ([[[self.fetchedResultsController sections] objectAtIndex:indexPath.section] numberOfObjects] == 0)
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:indexPath.section] withRowAnimation:UITableViewRowAnimationFade];
[self performFetch];
【讨论】：
感谢@Inafziger，添加代码会导致错误：“UITableView 没有可见界面声明选择器 deleteSections”... 糟糕，对不起，我忘记了其余的功能...查看我的更新。以上是关于当我删除核心数据实体的最后一条记录时，为啥我的应用程序崩溃了？的主要内容，如果未能解决你的问题，请参考以下文章
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