how to make a route+handler that accepts an optional value parameter?

[dan-da]

So I have URLs that accept a selector field that may or may not accept another argument. In this (contrived) example the second path element is the selector and the 3rd element (if present) is a value that only pertains to certain selectors:

        /person/ceo
        /person/cfo
        /person/id/45224
        /person/hash/fa234cad452cd45

And I have a PersonSelector struct that can accept any of these forms and convert it into a canonical PersonIdentifier.

note that there are basically two url forms: /person/selector and /person/selector/value

I would like to define a single route for "/person" that can handle either variant, passing the selector and optional value into PersonSelector. Alternatively, two routes that call a single handler fn.

I haven't figured out how to make that work. So I resorted to defining two routes that call two separate handler fn, and then each handler calls a common worker fn. This works perfectly, but seems rather inelegant, especially as the pattern is repeated a few times.

        .route("/person/:selector", get(person_page))
        .route("/person/:selector/:value", get(person_page_with_value))

So I guess my question boils down to: is there a way to make the person route and person_page handler optionally accept a value?

[jplatte]

In general, I would recommend that you just have two handler function that delegate most of their work to the same private function that is never used as a handler directly. However, both of the things you are asking can be achieved to some extent:

• If you want to only call .route once to register a handler for _anything starting with /person/, you can do so with .route("/person/*rest", get(handler)); there is no syntax for limiting the number of trailing segments though
• If you want to extract either one or two path parameters with axum::extract::Path<T>, then T has to be a type that implements Deserialize such that both inputs work, for example you could use Path<Vec<String>> for an arbitrary number of parameters, or a custom type like this for the two routes shown in your example:

  #[derive(Deserialize)]
  struct PersonPathParams {
      selector: String,
      value: Option<String>,
  }

[dan-da]

that is very helpful, thank-you! I haven't tried it yet, but it seems combining the two techniques should achieve the desired result.

[dan-da]

Just reporting back that I was able to combine these techniques and it is working perfectly with a single route and single handler for each page. This keeps both the routes and handlers simpler for anyone reading the code.

thx again @jplatte for the suggestions.