In Rust, is there a way to iterate through the values of an enum?

Question

I come from a Java background and I might have something like enum Direction { NORTH, SOUTH, EAST, WEST} and I could do something with each of the values in tur

Answer 1

If you do not want to import a third-party crate, you can make your own macro to do so. Here is how I achieved it (there are probably ways to improve this):

macro_rules! iterable_enum {
    ($visibility:vis, $name:ident, $($member:tt),*) => {
        $visibility enum $name {$($member),*}
        impl $name {
            fn iterate() -> Vec<$name> {
                vec![$($name::$member,)*]
            }
        }
    };
    ($name:ident, $($member:tt),*) => {
        iterable_enum!(, $name, $($member),*)
    };
}

And then you can do:

iterable_enum!(pub, EnumName, Value1, Value2, Value3);

fn main() {
    for member in EnumName::iterate() {
        // ...
    }
}

This implementation is limited to simple enums. Consider the following enum, how would you iterate over it?:

enum MoreComplexEnum {
    One(T1),
    Two(T2),
    Other,
    Both(T1, T2),
    Error(String),
}

Because of the power of enums in Rust, it can be difficult to implement a perfectly iterable enum, since they are not like the simple enums you have in C or Java.