Now, in web application I'm trying to use actix-protobuf in order to return data as follows.
let data: Items = ...
return HttpResponse::Ok().protobuf(data);
At this point I'm getting an error
the trait `prost::message::Message` is not implemented for `Items`
In the protobuf example (Actix examples - protobuf), they're using Message from prost-derive crate..
(So it looks like there's prost::Message as well as prost::message::Message. )
What do you have in the [dependencies] section of your Cargo.toml? Sometimes confusing errors like this arise when you inadvertently depend on two incompatible versions of the same crate.
Right, because the version of actix-protobuf you're using depends on prost ^0.8.0, so if you don't specify a version that's compatible with that (as 0.9.0 is not) then you will get both versions.