What would an implementation of an optional parameter look like?

[ilantoren]

I have an application I am building in order to learn more about Rocket/Rust with MongoDB. The MongoDB part is fine but I want a call something like this:

#[get("/restaurants_docs/<neighborhood>/<cuisines>",   format="json" )]
async fn restaurants_docs(client: &State<Box<Client>>, neighborhood: &str, cuisines: Option<&str>) -> Json<Bson> {
    let cuisine_array: Option<Vec<&str>> = match cuisines {
        Some( item ) => {
            let  split = item.split(",");
            let cuisine_array =split.collect::<Vec<&str>>();
            Some( cuisine_array )
        },
        None => None
    };

    let bson =  restaurants_by_neighborhood_docs(client, neighborhood, cuisine_array).await;
    Json(Bson::from(bson) )
}

The problem is that when cuisines is missing then the REQ fails as it doesn't match. Is there an example where this is shown?

Thanks
Mongo Loves Data - Rocket

[ilantoren]

From the code,q there is this (./core/lib/src/request/from_param.rs):

impl<'r, T: FromSegments<'r>> FromSegments<'r> for Option<T> {
    type Error = std::convert::Infallible;

    #[inline]
    fn from_segments(segments: Segments<'r, Path>) -> Result<Option<T>, Self::Error> {
        match T::from_segments(segments) {
            Ok(val) => Ok(Some(val)),
            Err(_) => Ok(None)
        }
    }
}

So if the type is Vec or Vec(str) there need to be an implementation FromSegements for that type (String/str). But how?