Lib.rs

属性宏，为您的枚举实现From特质。

use from_num::from_num;
#[derive(Debug,PartialEq)]
#[from_num(i8,u64,usize)]
enum Planet {
    Mercury,
    Venus,
    Earth,
    Mars,
    Jupiter = 0b1000,
    Saturn,
    Uranus = 0xff,
    Neptune
}
pub fn get_from_number() {
    assert_eq!(Planet::Jupiter,Planet::from_i8(0b1000 as i8).unwrap());
    assert_eq!(Planet::Neptune,Planet::from_u64(256 as u64).unwrap());
}