CODEWITHSUNDEEP
rustmetaprogramming
Edward
Edward

Reputation: 567

How do I iterate through the types that implement a trait

I am dealing with currencies.

I want to be able to parse them from ticker symbols like "USD".

I have implemented a currency trait which I want to have a compile time ticker symbol.

I want to iterate through all the types that implement Currency to check if their ticker symbol is equal to the string being parsed. If so, I want to return a type of that currency.

I have this so far:

pub trait Currency {
    const TICKER_SYMBOL: String;
}

#[derive(debug)]
struct USD;
impl Currency for USD { const TICKER_SYMBOL:  String = "USD".to_string();}

impl FromStr for dyn Currency {
    type Err = &'static str;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        todo!()
    }
}

Upvotes: 0

Views: 486

Answers (1)

Edward
Edward

Reputation: 567

The strum crate + enums gave me what I wanted.

use std::str::FromStr;
use strum_macros::EnumString;

#[derive(Debug, PartialEq, EnumString)]
enum Currency {
    USD,
    BTC
}

#[test]
fn parses_currencies() {
    let c = Currency::from_str("USD");
    assert_eq!(Ok(Currency::USD), c);
    let err = Currency::from_str("monopoly money");
    assert!(err.is_err());
}

Upvotes: 2

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