How do swap the indexes of a Posts?-CodePudding

I have model with order indices, for example - 1, 2, 3, 5, 8, 10... (empty indices were allegedly removed - 4, 6, 7, 9...)

I need to get the index and swap it with the nearest index next to it. (for Up and Down move).

What I have:

def set_order_index(item: Posts, distinction: int):
    items_to_swap = Posts.objects.filter(
        order_index=item.order_index   distinction)
    if len(items_to_swap) > 0:
        item_to_swap = items_to_swap[0]
        item_to_swap.order_index = item.order_index
        item_to_swap.save()
    item.order_index  = distinction
    item.save()

And for Up views ' 1':

def up_item(request, id):
    item = Posts.objects.get(id=id)
    set_order_index(item,  1)
    return redirect('index')

And for Down '-1'...

But my set_order_index only does 1 and -1 always, and if it gets the same value, then swaps places. That is if index 3, the set_order_index will only make 4 ( 1), but I need to swap 3 with 5. Because there is no index 4.

And if I use Post with index 10 to Down - I need to swap with 8, but my set_order_index only do -1, and I get only 9. But I need 10 to swap with 8 immediately.

In my head, I understand how to do this through QuerySet, getting the indices of all that is > and < and then select the first or last - it is necessary, the neighbor. But in the code, I can't do it for it to work.

CodePudding user response：

def swap_up(item):
    nextItem = Posts.objects.filter(order_index__gt=item.order_index).order_by('order_index').first()
    if nextItem:
        item_index = item.order_index
        item.order_index = nextItem.order_index
        nextItem.order_index = item_index

        item.save()
        nextItem.save()

def swap_down(item):
    prevItem = Posts.objects.filter(order_index__lt=item.order_index).order_by('order_index').last()
    if prevItem:
        item_index = item.order_index
        item.order_index = prevItem.order_index
        prevItem.order_index = item_index

        item.save()
        prevItem.save()