How do I pass an EnumMap to a function?

Question

Goal:
To pass an EnumMap from the enum_map crate to a function

My error:

25 | fn print_board(board: &[CellStatus], celldict: & EnumMap<&CellStatus, &str>){
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait EnumArray<&str> is not implemented for &CellStatus

Relevant code:

use enum_map::{enum_map, EnumMap};

enum CellStatus{
    Empty,
    Cross,
    Circle,
}

fn print_board(board: &[CellStatus], celldict: & EnumMap<&CellStatus, &str>){
    for cell in board {
        println!("{}", celldict[cell]);

    }
}



fn main() {


    let cell_repr = enum_map! {
        CellStatus::Empty  => " _ ".to_string(),
        CellStatus::Cross  => " X ".to_string(),
        CellStatus::Circle => " O ".to_string(),
    };


}

Background:

Im trying to make a simple tic-tac-toe game as my first rust script. I havent implemented the logic yet of the game. I could make it work by just passing integers and a bunch of if statements but i wanted to write it in a more clean way.

Im guessing I have to implement something for my enum? but im not sure how to go about doing that.

Full code: https://pastebin.com/pZwqyvR2
Crate in question: https://docs.rs/enum-map/latest/enum_map/#

Answer 1

According to the documentation you posted, you have to derive the crate's trait in order to use enum_map! on that enum. The only modification is just before your enum definition:

#[derive(Enum)]
enum CellStatus {
  Empty,
  Cross,
  Circle,
}

Also, the result of enum_map! is a EnumMap<CellStatus, String> in your case, not a EnumMap<&CellStatus, &str>, Changing into that type should help. It complains that &CellStatus does not implement a certain trait because that trait is automatically implemented by the derive macro for CellStatus, and not for &CellStatus. However, if you do this it will still not compile, because EnumMap does not implement Index<&CellStatus>, but only Index<CellStatus> (which is a bit stupid if you ask me). Anyways, the best way to patch this IMO is to make CellStatus Copy. The following compiles:

use enum_map::{enum_map, Enum, EnumMap};

#[derive(Enum, Clone, Copy)]
enum CellStatus {
    Empty,
    Cross,
    Circle,
}

fn print_board(board: &[CellStatus], celldict: &EnumMap<CellStatus, String>){
    for cell in board {
        println!("{}", celldict[*cell]);

    }
}

fn main() {
    let cell_repr = enum_map! {
        CellStatus::Empty => String::from("_"),
        CellStatus::Cross => String::from("X"),
        CellStatus::Circle => String::from("O"),
    };
}