Extracting UrlParams

[nyarly]

Summary

I'm experimenting with an authorization framework, and I'd like to be able to extract facts about a general request in order to apply policy to it. Being able to consider the path params of a request would be very helpful.

I see #154, where the UrlParams extractor was removed, and that the UrlParams extension has been made crate(public), but the reasoning behind that change isn't clear. The PR body says "use extract::Path" instead, but to do that I need to know how many parameters are in the path - which is sensible for the author of the Router and Handler, but as a middleware author that doesn't make sense.

Is there a different approach for extracting some unknown number of path parameters, perhaps equivalent to how the Query extractor can fill a Vec?

axum version

0.7.5

[nyarly]

Aha - just found extract::RawPathParams that seems to do what I need.

[jplatte]

Right, I always forget that's a thing ^^
That should be more efficient than my first two suggestions.

[jplatte]

Yes, you can extract all path parameters using Path<Vec<String>> if you just want the values, Path<BTreeMap<String, String>> (or HashMap) if you want a map of parameter names and values. You can even do

#[derive(Deserialize)]
struct Parameters {
    foo_id: Option<Uuid>,
    bar_id: Option<Uuid>,
    name: Option<String>,
}

// you can use `Path(params): Path<Parameters>` and if the route has a `foo_id` param,
// `params.foo_id` will have the deserialized parameter value