如何结合CoreData给UITableView的section填充数据

搬运自StackOverFlow：numberOfRowsInSection: method for core data and multiple sections‘

问题描述：一个tableview中建立两个section，第一个section使用NSArray填充数据，第二个section使用coredata填充数据

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
if (section == 0) {
return 1;
} else {
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
}
}

最开始的代码返回错误
Terminating app due to uncaught exception 'NSRangeException', reason: '* -[__NSArrayM objectAtIndex:]: index 1 beyond bounds [0 .. 0]'

解决方法：
- (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];
}
}

原因解释：
coredata中的fetched results controller只有一个section(section #0)，但我们却想在第二个section(section
#1)里面显示FRC所取得的数据

在cellforrow这个方法里也要对section的数字减一

- (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;
}
}