NSMutableArray不记得对象的位置

Question

我创建了一个NSMutableArray类别。我只想移动我的数组中的对象，当它们在我的表视图中移动时。这是我的类别：

- (void)moveObjectFromIndex:(NSUInteger)from toIndex:(NSUInteger)to

{
if (to != from) {
    id obj = [self objectAtIndex:from];
    [self removeObjectAtIndex:from];
    if (to >= [self count]) {
        [self addObject:obj];
    } else {
        [self insertObject:obj atIndex:to];
    }
  }
}

在我的视图控制器中，我打电话：

- (void)tableView:(UITableView *)table moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath
{
[self.tableArray moveObjectFromIndex:[sourceIndexPath row] toIndex:[destinationIndexPath row]];

[self.ammoTable reloadData];

}

但阵列似乎并没有在其周围移动物体。这可能是什么原因？我跟着这个tutorial。它应该工作，如果有人可以告诉问题，请高兴我的原因。非常感谢！

修改

我也尝试过下面的代码，遗憾的是它不起作用：

- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
    // fetch the object at the row being moved
NSString *r = [self.tableArray objectAtIndex:fromIndexPath.row];

    // remove the original from the data structure
[self.tableArray removeObjectAtIndex:fromIndexPath.row];

    // insert the object at the target row
[self.tableArray insertObject:r atIndex:toIndexPath.row];

[self.ammoTable reloadData];
}

再次编辑

CellForRow：

-(UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
static NSString * identifier = @"identifier";

self.cell = [tableView dequeueReusableCellWithIdentifier:identifier];


HandgunAmmo *handgunAmmo = [self.tableArray objectAtIndex:indexPath.row];
self.cell.brandLabel.text = handgunAmmo.brand;
self.cell.caliberLabel.text = handgunAmmo.caliber;
self.cell.numberOfRoundsLabel.text = handgunAmmo.numberOfRounds;

return self.cell;
}

更新

-(void)viewWillAppear:(BOOL)animated{
if (self.context == nil)
{
    self.context = [(RootAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
}
NSFetchRequest *request = [[NSFetchRequest alloc]init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"HandgunAmmo" inManagedObjectContext:self.context];
[request setEntity:entity];
NSError *error;
NSMutableArray *array = [[self.context executeFetchRequest:request error:&error] mutableCopy];
[self setTableArray:array];
[self.ammoTable reloadData];
[super viewWillAppear:YES];
}

//上面，我加载我的核心数据。

我不打电话

-(void)viewWillDisappear;