How to get struct field names in Rust? [duplicate]

Question

Is there some equivalent of JS's Object.keys() for Rust's struct?

I need something to generate CSV headers (I use rust-csv) from structure field names.

struct Export {
    first_name: String,
    last_name: String,
    gender: String,
    date_of_birth: String,
    address: String
}

//... some code

let mut wrtr = Writer::from_file("/home/me/export.csv").unwrap().delimiter(b'\t');

wrtr.encode(/* WHAT TO WRITE HERE TO GET STRUCT NAMES as tuple of strings or somethings */).is_ok()

Answer 1

The current main method of metaprogramming in Rust is via macros. In this case, you can capture all the field names and then add a method that returns string forms of them:

macro_rules! zoom_and_enhance {
    (struct $name:ident { $($fname:ident : $ftype:ty),* }) => {
        struct $name {
            $($fname : $ftype),*
        }

        impl $name {
            fn field_names() -> &'static [&'static str] {
                static NAMES: &'static [&'static str] = &[$(stringify!($fname)),*];
                NAMES
            }
        }
    }
}

zoom_and_enhance!{
struct Export {
    first_name: String,
    last_name: String,
    gender: String,
    date_of_birth: String,
    address: String
}
}

fn main() {
    println!("{:?}", Export::field_names());
}

For advanced macros, be sure to check out The Little Book of Rust Macros.