quest – Rust: Combinators

Applied Intermediate

13 Combinators

Most match statements on Option have a one-word replacement. Transform the inside of an Option with map, then fold a whole parse-with-default flow into a single chain.

Step 2 / 2

In port, parse the configured port or fall back to 8080 -- one chain, no branches.

Hints

and_then chains a step that itself returns an Option; parse().ok() is exactly that.
Finish with .unwrap_or(8080).

13_combinators.rs

// the parsed port if present and valid, else 8080 -- one chain
fn port(config: Option<&str>) -> u16 {
    todo!()
}

Reset to starterCompiled in a sandbox; hidden checks must pass.

Reveal solution

fn port(config: Option<&str>) -> u16 {
    config.and_then(|s| s.parse().ok()).unwrap_or(8080)
}