numberOfRowsInSection：核心数据和多个部分的方法 [英] numberOfRowsInSection: method for core data and multiple sections
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问题描述
我试图显示一个有两个部分的表视图。第一部分将始终具有1行，第二部分将具有与数据点一样多的行。我使用Core Data和以下tableView：numberOfRowsInSection：method ...
- （NSInteger）tableView：（UITableView *） tableView numberOfRowsInSection：（NSInteger）section
{
if（section == 0）{
return 1;
} else {
id< NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex：section];
return [sectionInfo numberOfObjects];但是，我收到以下错误：
<$>
由于未捕获异常NSRangeException而终止应用程序，原因：
' * - [__ NSArrayM objectAtIndex： ]：index 1 beyond bounds [0 .. 0]'
任何帮助将不胜感激。非常感谢。
新-------------------------------- -----------------------------------------------
这是当前实现的相关方法：
- （NSInteger） tableView：（UITableView *）tableView numberOfRowsInSection：（NSInteger）section
{
if（section == 0）{
return 1;
} else {
NSUInteger frcSection = section - 1;
id< NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex：frcSection];
return [sectionInfo numberOfObjects];
}
}
- （UITableViewCell *）tableView：（UITableView *）tableView cellForRowAtIndexPath：（NSIndexPath *）indexPath
{
static NSString * CellIdentifier = @Cell;
UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier：CellIdentifier];
if（cell == nil）{
cell = [[UITableViewCell alloc] initWithStyle：UITableViewCellStyleDefault reuseIdentifier：CellIdentifier];
}
[self configureCell：cell atIndexPath：indexPath];
return cell;
}
- （void）configureCell：（UITableViewCell *）cell atIndexPath：（NSIndexPath *）indexPath
{
if（indexPath.section == 0）{
cell.textLabel.text = entityOne.name; //从以前的VC传递的entityOne对象
} else {
entityTwo = [self.fetchedResultsController objectAtIndexPath：indexPath];
cell.textLabel.text = entityTwo.name;
}
}
- （void）controller：（NSFetchedResultsController *）controller
didChangeSection：（id< NSFetchedResultsSectionInfo>）sectionInfo
atIndex NSUInteger）sectionIndex
forChangeType：（NSFetchedResultsChangeType）type
{
NSUInteger frcSectionIndex = 0;
frcSectionIndex = sectionIndex + 1;
switch（type）{
case NSFetchedResultsChangeInsert：
[self.tableView insertSections：[NSIndexSet indexSetWithIndex：frcSectionIndex] withRowAnimation：UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete：
[self.tableView deleteSections：[NSIndexSet indexSetWithIndex：frcSectionIndex] withRowAnimation：UITableViewRowAnimationFade];
break;
}
}
- （void）controller：（NSFetchedResultsController *）controller
didChangeObject：（id）anObject
atIndexPath：（NSIndexPath *）indexPath
forChangeType：（NSFetchedResultsChangeType）type
newIndexPath：（NSIndexPath *）newIndexPath
{
UITableView * tableView = self.tableView;
switch（type）{
case NSFetchedResultsChangeInsert：
[tableView insertRowsAtIndexPaths：@ [newIndexPath] withRowAnimation：UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete：
[tableView deleteRowsAtIndexPaths：@ [indexPath] withRowAnimation：UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate：
[self configureCell：[tableView cellForRowAtIndexPath：indexPath] atIndexPath：indexPath];
break;
case NSFetchedResultsChangeMove：
[tableView deleteRowsAtIndexPaths：@ [indexPath] withRowAnimation：UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths：@ [newIndexPath] withRowAnimation：UITableViewRowAnimationFade];
break;
}
}
解决方案原因是抓取结果控制器（FRC）只有一个部分（部分＃0 ），您希望在第二部分（部分＃1 ）中显示表视图。
这是可能的，但您必须在FRC节号和表视图节号之间映射，例如
- （NSInteger）tableView：（UITableView *）tableView numberOfRowsInSection：（NSInteger）section
{
if（section == 0）{
return 1;
} else {
NSUInteger frcSection = section - 1;
id< NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex：frcSection];
return [sectionInfo numberOfObjects];
}
}
在 cellForRowAtIndexPath 。
在FRC委托方法 didChangeObject ， didChangeSection 您必须在调用表视图方法之前（例如 insertRowsAtIndexPaths ）向节号添加1 。
ADDED： configureCell 像这样：
- （void）configureCell：（UITableViewCell *）cell atIndexPath：（NSIndexPath *）indexPath
{
if（indexPath.section == 0）{
cell.textLabel.text = entityOne.name; //从上一个VC传递的entityOne对象
} else {
NSIndexPath * frcIndexPath = [NSIndexPath indexPathForRow：indexPath.row inSection：（indexPath.section - 1）];
entityTwo = [self.fetchedResultsController objectAtIndexPath：frcIndexPath];
cell.textLabel.text = entityTwo.name;
}
}
和 didChangeObject 这样：
- （void）controller：（NSFetchedResultsController *）controller
didChangeObject： ）anObject
atIndexPath：（NSIndexPath *）indexPath
forChangeType：（NSFetchedResultsChangeType）type
newIndexPath：（NSIndexPath *）newIndexPath
{
UITableView * tableView = self.tableView ;
NSIndexPath * tvIndexPath = [NSIndexPath indexPathForRow：indexPath.row inSection：（indexPath.section + 1）];
NSIndexPath * tvNewIndexPath = [NSIndexPath indexPathForRow：newIndexPath.row inSection：（newIndexPath.section + 1）];
switch（type）{
case NSFetchedResultsChangeInsert：
[tableView insertRowsAtIndexPaths：@ [tvNewIndexPath] withRowAnimation：UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete：
[tableView deleteRowsAtIndexPaths：@ [tvIndexPath] withRowAnimation：UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate：
[self configureCell：[tableView cellForRowAtIndexPath：tvIndexPath] atIndexPath：tvIndexPath];
break;
case NSFetchedResultsChangeMove：
[tableView deleteRowsAtIndexPaths：@ [tvIndexPath] withRowAnimation：UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths：@ [tvNewIndexPath] withRowAnimation：UITableViewRowAnimationFade];
break;
}
}
您可能会有这样的想法：
- 从FRC索引路径转到表视图索引路径时，请向该部分添加一个。
- 查看FRC索引路径的索引路径，从该部分中减去1。
I am trying to show a table view with 2 sections. The first section will always have 1 row and the second section will have as many rows as data points. I am using Core Data and the following tableView:numberOfRowsInSection: method...
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
if (section == 0) {
return 1;
} else {
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
}
}
However, I am getting the following error:
Terminating app due to uncaught exception 'NSRangeException', reason:
'* -[__NSArrayM objectAtIndex:]: index 1 beyond bounds [0 .. 0]'
Any help will be appreciated. Thanks.
NEW -------------------------------------------------------------------------------
This is the current implementation of the relevant methods:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
if (section == 0) {
return 1;
} else {
NSUInteger frcSection = section - 1;
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:frcSection];
return [sectionInfo numberOfObjects];
}
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
[self configureCell:cell atIndexPath:indexPath];
return cell;
}
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.section == 0) {
cell.textLabel.text = entityOne.name; //entityOne object passed from previous VC
} else {
entityTwo = [self.fetchedResultsController objectAtIndexPath:indexPath];
cell.textLabel.text = entityTwo.name;
}
}
- (void)controller:(NSFetchedResultsController *)controller
didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex
forChangeType:(NSFetchedResultsChangeType)type
{
NSUInteger frcSectionIndex = 0;
frcSectionIndex = sectionIndex + 1;
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:frcSectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:frcSectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller
didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath
forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
解决方案 The reason is that the fetched results controller (FRC) has only one section (section #0), which you want to be displayed in the second section (section #1) of the table view.
This is possible, but you have to map between FRC section numbers and table view section numbers, e.g.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
if (section == 0) {
return 1;
} else {
NSUInteger frcSection = section - 1;
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:frcSection];
return [sectionInfo numberOfObjects];
}
}
The same mapping is necessary in cellForRowAtIndexPath.
In the FRC delegate methods didChangeObject, didChangeSection you have to add 1 to the section number before calling the table view methods (e.g. insertRowsAtIndexPaths).
ADDED: configureCell should look like this:
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.section == 0) {
cell.textLabel.text = entityOne.name; //entityOne object passed from previous VC
} else {
NSIndexPath *frcIndexPath = [NSIndexPath indexPathForRow:indexPath.row inSection:(indexPath.section - 1)];
entityTwo = [self.fetchedResultsController objectAtIndexPath:frcIndexPath];
cell.textLabel.text = entityTwo.name;
}
}
and didChangeObject like this:
- (void)controller:(NSFetchedResultsController *)controller
didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath
forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
UITableView *tableView = self.tableView;
NSIndexPath *tvIndexPath = [NSIndexPath indexPathForRow:indexPath.row inSection:(indexPath.section + 1)];
NSIndexPath *tvNewIndexPath = [NSIndexPath indexPathForRow:newIndexPath.row inSection:(newIndexPath.section + 1)];
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:@[tvNewIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:@[tvIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:tvIndexPath] atIndexPath:tvIndexPath];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:@[tvIndexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:@[tvNewIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
You probably get the idea:
- When going from FRC index path to table view index path, add one to the section.
- When going from table view index path to FRC index path, subtract one from the section.
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