如何在特征中使用枚举并在枚举中的结构上实现特征？ Rust

Question

I'm learning Rust so this might be a duplicate, since I'm still not sure how to search this. I tried to make a enum that contains different structs and since those structs have same methods but different implementation, I can't figure out how to properly write the types for the trait and the implementation. This is what I have so far:

struct Vector2 {
    x: f32,
    y: f32,
}

struct Vector3 {
    x: f32,
    y: f32,
    z: f32,
}

enum Vector {
    Vector2(Vector2),
    Vector3(Vector3),
}

trait VectorAdd {
    fn add(&self, other: &Vector) -> Vector;
}

impl VectorAdd for Vector2 {
    fn add(&self, other: &Vector2) -> Vector2 {
        Vector2 {
            x: self.x + other.x,
            y: self.y + other.y
        }
    }
}

This code does not compile, and the error messages don't make it clearer for me. Anyone can guide me how to write this properly? or if it's even possible?

Answer 1

Since you are using generics here, you don't need the enum to write the trait:

struct Vector2 {
    x: f32,
    y: f32,
}

struct Vector3 {
    x: f32,
    y: f32,
    z: f32,
}

trait VectorAdd {
    fn add(&self, other: &Self) -> Self;
}

impl VectorAdd for Vector2 {
    fn add(&self, other: &Vector2) -> Vector2 {
        Vector2 {
            x: self.x + other.x,
            y: self.y + other.y,
        }
    }
}

impl VectorAdd for Vector3 {
    fn add(&self, other: &Vector3) -> Vector3 {
        Vector3 {
            x: self.x + other.x,
            y: self.y + other.y,
            z: self.z + other.z,
        }
    }
}

( playground )

You can implement the enum based on this definition:

enum Vector {
    Vector2(Vector2),
    Vector3(Vector3),
}

impl VectorAdd for Vector {
    fn add(&self, other: &Vector) -> Vector {
        match (self, other) {
            (Self::Vector2(a), Self::Vector2(b)) => Self::Vector2(a.add(b)),
            (Self::Vector3(a), Self::Vector3(b)) => Self::Vector3(a.add(b)),
            _ => panic!("invalid operands to Vector::add"),
        }
    }
}

Macros may help you if the number of variants gets large.