Question

实现这一目标的最简单方法是什么？

enum E {
    A,
    B,
    C,
}

// Should return "A" for 0, "B" for 1 and "C" for 2
fn convert(i: u32) -> str {
    // ???
}

Answer 1

您无法返回str，但可以返回&str。结合How do I match enum values with an integer?和Get enum as string的想法：

#[macro_use]
extern crate strum_macros;
extern crate strum;

use strum::IntoEnumIterator;

#[derive(EnumIter, AsRefStr)]
enum E {
    A,
    B,
    C,
}

fn main() {
    let e = E::iter().nth(2);
    assert_eq!(e.as_ref().map(|e| e.as_ref()), Some("C"));
}

Answer 2

有必要添加#[derive(Debug)]属性并在枚举上定义一个实现：

#[derive(Debug)]
#[derive(Copy, Clone)]
enum E {
    A,
    B,
    C,
}

impl E {
    fn from(t: u8) -> E {
        assert(t<=enum_to_int(E::C), "Enum range check failed!");
        let el: E = unsafe { std::mem::transmute(t) };
        return el;
    }
    fn to_string(&self) -> String {
        return format!("{:?}", self);
    }

    fn string_from_int(t: u8) -> String {
        return E::from(t).to_string();
    }
}


fn enum_to_int(el: &E) -> u8 {
    *el as u8
}

然后可以像这样使用：

fn main() {
    let s = E::string_from_int(3 as u8);
    println!("{}", s);
}

如何在特定索引处返回枚举字符串？

2 个答案: