04_02_validate_derive/
04_02_validate.rs

1use std::ops::RangeInclusive;
2
3use clap::Parser;
4
5#[derive(Parser)]
6#[command(version, about, long_about = None)]
7struct Cli {
8    /// Network port to use
9    #[arg(value_parser = port_in_range)]
10    port: u16,
11}
12
13fn main() {
14    let cli = Cli::parse();
15
16    println!("PORT = {}", cli.port);
17}
18
19const PORT_RANGE: RangeInclusive<usize> = 1..=65535;
20
21fn port_in_range(s: &str) -> Result<u16, String> {
22    let port: usize = s
23        .parse()
24        .map_err(|_| format!("`{s}` isn't a port number"))?;
25    if PORT_RANGE.contains(&port) {
26        Ok(port as u16)
27    } else {
28        Err(format!(
29            "port not in range {}-{}",
30            PORT_RANGE.start(),
31            PORT_RANGE.end()
32        ))
33    }
34}