一个数据表对象(NSManagedObject)加入排序

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

//在这种方法里操作

- (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，第二种是下移

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（依照order的升序排列）。把删除数据以下的数据对象的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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