Rust 宏

标准库提供的宏

env! 硬编码方式读取包信息

@see https://github.com/mookid/broken_utils/blob/master/rust/ff/src/main.rs

const BIN_NAME: &str = env!("CARGO_PKG_NAME");
const VERSION: &str = env!("CARGO_PKG_VERSION");

json!

macro_rules! json {
    ($($key: ident : $value: expr), *) => {{
        let mut map = std::collections::HashMap::new();
        $(
            map.insert(stringify!($key), $value.clone());
        )*
        map
    }};
}

fn main() {
    let user = json! {
        name: "张三",
        age: "18岁"
    };
    println!("{:?}", user);

    let obj = json! {
        id: 0.3_f64,
        value: 0.1+0.2
    };
    println!("{:?}", obj);
}

json! 允许逗号可有可无

macro_rules! json {
    ($($key: ident : $value: expr$(,)*)*) => {{
        let mut map = std::collections::HashMap::new();
        $(
            map.insert(stringify!($key), $value.clone());
        )*
        map
    }};
}

fn main() {
    let user = json! {
        name: "张三"
        age: "18岁"
    };
    println!("{:?}", user);

    let obj = json! {
        id: 0.3_f64,,,,
        value: 0.1+0.2
    };
    println!("{:?}", obj);
}

json! 允许最后一行逗号可有可无

macro_rules! json {
    ($($key: ident : $value: expr),* $(,)*) => {{
        let mut map = std::collections::HashMap::new();
        $(
            map.insert(stringify!($key), $value.clone());
        )*
        map
    }};
}

fn main() {
    let user = json! {
        name: "张三",
        age: "18岁",
    };
    println!("{:?}", user);

    let obj = json! {
        id: 0.3_f64,
        value: 0.1+0.2,,,
    };
    println!("{:?}", obj);
}

END