Is there a way to use existing structs as enum variants?

Question

I'm using an enum for polymorphism, similar to the following:

enum MyType {
    Variant1 { a: i32, b: i32 },
    Variant2 { a: bool, b: bool },
}

Is there clean way to use existing structs for Variant1 and Variant2? I've done the following:

struct Variant1 {
    a: i32,
    b: i32,
}

struct Variant2 {
    a: bool,
    b: bool,
}

enum MyType {
    Variant1(Variant1),
    Variant2(Variant2),
}

but it feels pretty clunky. I was wondering if there's a better way to accomplish a similar thing.

https://keepcalmandlearnrust.com/2017/03/polymorphism-in-rust-enum-vs-trait-struct/ — anderspitman, Apr 07 '18 at 08:18

score 15 · Accepted Answer · edited Mar 18 '20 at 18:11

15

There have been multiple RFCs about making enum variants their own type:

Unfortunately, they have been postponed or not yet decided on as this is not considered a language priority.

This means that right now, the way you have proposed is the only way to have types for enum variants.

edited Mar 18 '20 at 18:11

Shepmaster

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answered Apr 07 '18 at 10:19

mcarton

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Can the boilerplate be reduced / sugared a little with macros then? Or is it too complicated because they would span accross `enum` *and* `struct` *and* maybe [traits](https://stackoverflow.com/q/51567350/3719101) definitions ? – iago-lito May 24 '19 at 10:51

score 2 · Answer 2 · answered Apr 07 '18 at 07:38

2

No, that's exactly how that works.

answered Apr 07 '18 at 07:38

Sebastian Redl

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Is there a way to use existing structs as enum variants?

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