为数据表对象(NSManagedObject)添加排序
eg:数据库表对象
@interface Meditation : NSManagedObject
@property (nonatomic, retain) NSString * order;//用来排序的属性值，用0、1、2、3...排序
@end
//在这个方法里操作
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath
{
Meditation *sourceMeditation=[self.dataSource objectAtIndex:sourceIndexPath.row];
sourceMeditation.order =[NSString stringWithFormat:@"%i",destinationIndexPath.row];
[sourceMeditation.managedObjectContext save:nil];
//两种情况一种是上移，另外一种是下移1.sourceIndexPath.row>destinationIndexPath.row
2.sourceIndexPath.row>destinationIndexPath.row
if (sourceIndexPath.row < destinationIndexPath.row)
{
for (NSInteger i = sourceIndexPath.row+1; i <= destinationIndexPath.row; i ++)
{
Meditation *m = [self.dataSource objectAtIndex:i];
m.order =[NSString stringWithFormat:@"%i",[m.attribute6 integerValue]-1];
[sourceMeditation.managedObjectContext save:nil];
}
}else
{
for (NSInteger i = sourceIndexPath.row-1; i >= destinationIndexPath.row; i--)
{
Meditation *m = [self.dataSource objectAtIndex:i];
m.order =[NSString stringWithFormat:@"%i",[m.attribute6 integerValue]+1];
[sourceMeditation.managedObjectContext save:nil];
}
}
}
//当对象被删除的时候（按照order的升序排列），把删除数据下面的数据对象的order属性值-1
-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath{
if (editingStyle == UITableViewCellEditingStyleDelete) {
for (int i=indexPath.row; i<self.dataSource.count; i++) {
Meditation *m = [self.dataSource objectAtIndex:i];
m.order =[NSString stringWithFormat:@"%i",[m.attribute6 integerValue]-1];
[appDelegate saveContext];
}
}
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