I want to try and use Mapping with Sha2x256 or any other value that is large enough so that each of these will be unique.
I want mapping to be like this: unique_ids: Mapping <Sha2x256 ,u128>
Whenever I try to make Mapping <String, u128> I get an error "contract doesn't have a size known at compile-time"
So I'm trying anything else that can act as an unique id and will not repeat itself. It can be Sha2x256, Blake2s256 etc.
Does anyone have any advice?