Working with many_many_through relationships

Questions
1

Silverstripe Version: 4.5.1

Question:

I can’t get ModelAdmin to work with Many_Many_Through relationships. I’ve set up the example given here https://docs.silverstripe.org/en/4/developer_guides/model/relations/#many-many-through-relationship-joined-on-a-separate-dataobject

My ModelAdmin is set up as per https://docs.silverstripe.org/en/4/developer_guides/forms/field_types/gridfield/#many-many-extrafields

I’ve also tried specifying the ItemEditFormCallback as per SS4: edit many_many_extraFields in a GridField detail form - SilverStrip.es

The problem is the additional fields show, but do not load or save data.

Here’s a gist Teamp.php · GitHub

1 Like
2

What happens if you change (this line) ManyMany[Ranking] to Supporters[Ranking]?

I haven’t tried to do this before but I’m guessing the docs have an error and that the example code should have new TextField('Teams[Position]', 'Current Position') instead of new TextField('ManyMany[Position]', 'Current Position').

3

Hi Jono,

Yeah I’ve tried that as well - no difference.

4

I’ve found the problem, but not the solution (yet). The issue is the GridFieldDetailForm_ItemRequest only loads from the ManyMany array if the list is an instance of ManyManyList

ManyManyThroughList extends RelationList directly, so it’s not the correct instance.

5

Interesting. If you change that to $list instanceof ManyManyList || $list instanceof ManyManyThroughList does it work? Probably not that simple but you never know. There are likely other similar instances like that which might need updating, here’s another.

6

No, it doesn’t work because the ManyManyThroughList doesn’t have the getExtraData function.
I’ve raised a GitHub issue for it Gridfield does not load or save data from many many through relationships · Issue #9428 · silverstripe/silverstripe-framework · GitHub