Function actix_service::apply_fn

pub fn apply_fn<I, S, F, Fut, Req, In, Res, Err>(
    service: I, 
    wrap_fn: F
) -> Apply<S, F, Req, In, Res, Err> where
    I: IntoService<S, In>,
    S: Service<In, Error = Err>,
    F: Fn(Req, &S) -> Fut,
    Fut: Future<Output = Result<Res, Err>>, 

Apply transform function to a service.

The In and Out type params refer to the request and response types for the wrapped service.