Rust 将枚举序列化为字符串

示例

extern crate serde;
extern crate serde_json;

macro_rules! enum_str {
    ($name:ident { $($variant:ident($str:expr), )* }) => {
        #[derive(Clone, Copy, Debug, Eq, PartialEq)]
        pub enum $name {
            $($variant,)*
        }

        impl ::serde::Serialize for $name {
            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
                where S: ::serde::Serializer,
            {
                // 将枚举序列化为字符串。
                serializer.serialize_str(match *self {
                    $( $name::$variant => $str, )*
                })
            }
        }

        impl ::serde::Deserialize for $name {
            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
                where D: ::serde::Deserializer,
            {
                struct Visitor;

                impl ::serde::de::Visitor for Visitor {
                    type Value = $name;
                    
                    fn expecting(&self, formatter: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                        write!(formatter, "a string for {}", stringify!($name))
                    }

                    fn visit_str<E>(self, value: &str) -> Result<$name, E>
                        where E: ::serde::de::Error,
                    {
                        match value {
                            $( $str => Ok($name::$variant), )*
                            _ => Err(E::invalid_value(::serde::de::Unexpected::Other(
                                &format!("unknown {} variant: {}", stringify!($name), value)
                            ), &self)),
                        }
                    }
                }

                // 从字符串反序列化枚举。
                deserializer.deserialize_str(Visitor)
            }
        }
    }
}

enum_str!(LanguageCode {
    English("en"),
    Spanish("es"),
    Italian("it"),
    Japanese("ja"),
    Chinese("zh"),
});

fn main() {
    use LanguageCode::*;
    let languages = vec![English, Spanish, Italian, Japanese, Chinese];

    // Prints ["en","es","it","ja","zh"]
    println!("{}", serde_json::to_string(&languages).unwrap());

    let input = r#" "ja" "#;
    assert_eq!(Japanese, serde_json::from_str(input).unwrap());
}