Subgrid validation if it is't open

Hello,
I have a datatable with subgrid. Is there any way to validate subgrid, if it not open.
I have tried the subOpen function, but it not work.

Please see

https://webix.com/snippet/0c663be7

With promise using:

https://webix.com/snippet/eb7a12a6

The subgrid doesn’t exist before opening, so you can’t use API against the subgrid while it is not active. If you need to do some operations against the sub-data consider loading all data in the treecollection and sync datatable to it, in such case you will be able to access the child data through datacollection’s API and make some kind of custom validation.