Looks like your current validator will not allow a category to be used
twice in the entire item_category table, which is not consistent with a
many-to-many relationship. Is that your intention? Or do you instead want
to ensure that there are no duplicate item/category *combinations* in the
item_category table. If the latter, you can do something like the
following, which will not only provide the proper validation, but will also
limit the list of categories in the select widget to those that have not
already been paired with the current item:
def show_grid():
if 'item_category.item' in request.args:
item_id = int(request.args[request.args.index('item_category.item')
+ 1])
used_categories = db(db.item_category.item == item_id)._select(db.
item_category.category)
available_categories = db(~db.category.id.belongs(used_categories))
db.item_category.category.requires = IS_IN_DB(available_categories,
'category.id', '%(name)s')
grid = SQLFORM.smartgrid(db.item)
return dict(grid=grid)
In smartgrid, when you are viewing item-categories for a given item,
request.args will include "item_category.item", with the immediately
following arg being the id of the item being viewed. So, in the above code,
item_id is the id of the specific item in question. use_categories is a
query that determines which categories have already been paired with this
item in the item_categories table. It uses ._select so it can be passed to
.belongs as a subquery. available_categories is a Set object that
identifies categories that have *not* been paired with the current item in
item_categories. When you pass a Set object to IS_IN_DB, it restricts
values to records that are in the Set, so the validator will only allow
(and display in the form) categories not already assigned to the item.
Anthony
On Wednesday, December 14, 2016 at 5:31:11 PM UTC-5, icodk wrote:
>
> I have an item ,category and item_category tables facilitating many to
> many relations between items and categories, which enables an item to
> belongs to several categories. I use SQLSmartgrid to show the
> item_category table and to add categories to specific item. This all works
> well. I can even managed to get an error if I select an already selected
> category by using the following:
>
> db.item_category.category.requires = IS_IN_DB(db, 'category', '%(name)s',
> _and=IS_NOT_IN_DB(db, 'item_category.category', error_message=T('This
> category already assigned')), zero=None)
>
>
> So what more could I wish ?
>
> It would be nice if the category dropdown list I get when adding or editing
> category to an item would contains only the categories not yet assigned to
> the item I am working on
>
> At the moment I get a list with all categories, however selecting an
> existing category correctly give me an error as described above.
>
>
>
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