clap/examples/arg_enum_basic.rs

#[macro_use]
extern crate clap;

use clap::{App, Arg};

#[derive(ArgEnum, Debug)]
enum ArgChoice {
    Foo,
    Bar,
    Baz,
}

fn main() {
    let matches = App::new(env!("CARGO_PKG_NAME"))
        .arg(
            Arg::with_name("arg")
                .required(true)
                .takes_value(true)
                .possible_values(&ArgChoice::variants()),
        )
        .get_matches();

    let t = value_t!(matches.value_of("arg"), ArgChoice).unwrap_or_else(|e| e.exit());

    println!("{:?}", t);
}