More Rust macros

macros.rs

use std::collections::HashMap;

macro_rules! from_map {
    ($map: ident, $obj: ident, $field: ident) => {
        $obj.$field = $map.get(stringify!($field)).unwrap().to_string();
    };

    ($map: ident, $obj: ident, $head: ident, $($tail: ident), +) => {
        from_map!($map, $obj, $head);
        from_map!($map, $obj, $($tail), +);
    };
}

#[derive(Debug)]
struct Foo {
    aaa: String,
    bbb: String,
    ccc: String,
}

impl Default for Foo {
    fn default() -> Self {
        Self {
            aaa: String::from("DEFAULT"),
            bbb: String::from("DEFAULT"),
            ccc: String::from("DEFAULT"),
        }
    }
}

fn main() {
    let m = &[("aaa", "AAA"), ("bbb", "BBB"), ("ccc", "CCC")]
        .into_iter()
        .collect::<HashMap<_, _>>();

    let mut foo = Foo::default();
    println!("before={:#?}", foo);
    {
        from_map!(m, foo, aaa, bbb, ccc);
    }
    println!("after={:#?}", foo);
}