HowdoIimplementatraitforanenumanditsrespectivevariants?

一种可能的解决方案是为变体以及实施您的特征enum，正如您在此处看到的那样，它仅调用变体的特定实现：

use std::fmt;

struct NData {
    numeric: u32,
}

impl fmt::Display for NData {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.numeric)
    }
}

struct SData {
    strings: Vec,
}

impl fmt::Display for SData {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{:?}", self.strings)
    }
}

enum Data {
    N(NData),
    S(SData),
}

impl fmt::Display for Data {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Data::N(n_data) => n_data.fmt(f),
            Data::S(s_data) => s_data.fmt(f),
        }
    }
}

fn main() {
    let n = NData { numeric: 0xff };
    let s = SData { strings: vec!["hello".to_string(), "world".to_string()] };

    println!("{}", n);
    println!("{}", s);

    let d_n = Data::N(n);
    let d_s = Data::S(s);

    println!("{}", d_n);
    println!("{}", d_s);
}

255
["hello", "world"]
255
["hello", "world"]