捕獲組

extern crate regex;
use regex::Regex;

fn main() {
    let rg = Regex::new(r"was (\d+)").unwrap();
    // Regex::captures returns Option<Captures>,
    // first element is the full match and others
    // are capture groups
    match rg.captures("The year was 2016") {
        // Access captures groups via Captures::at
        // Prints Some("2016")
        Some(x) => println!("{:?}", x.at(1)),
        None    => unreachable!()
    }

    // Regex::captures also supports named capture groups
    let rg_w_named = Regex::new(r"was (?P<year>\d+)").unwrap();
    match rg_w_named.captures("The year was 2016") {
        // Named capures groups are accessed via Captures::name
        // Prints Some("2016")
        Some(x) => println!("{:?}", x.name("year")),
        None    => unreachable!()
    }

}