rustHow to use enum as hashmap key in Rust

Enums in Rust can be used as hashmap keys by implementing the Eq and Hash traits. This can be done by adding #[derive(Eq, Hash)] to the enum definition. For example:

#[derive(Eq, Hash)]
enum Color {
    Red,
    Blue,
    Green,
}

fn main() {
    use std::collections::HashMap;

    let mut colors = HashMap::new();
    colors.insert(Color::Red, "red");
    colors.insert(Color::Blue, "blue");
    colors.insert(Color::Green, "green");

    println!("{:?}", colors);
}

The output of this code is {Color::Red: "red", Color::Blue: "blue", Color::Green: "green"}. The #[derive(Eq, Hash)] annotation allows the enum to be used as a key in the hashmap.

Helpful links

• Rust Enums
• Rust HashMap
• Rust Derive

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