CODEWITHSUNDEEP
genericsrust
Sheosi
Sheosi

Reputation: 73

Embed generics inside struct

I find difficulties when using Rust traits, so for example which is the correct way to do this?

pub struct Cube<R>{
    pub vertex_data: [Vertex;24],
    pub asMesh: gfx::Mesh<R>
}

Upvotes: 4

Views: 917

Answers (1)

Shepmaster
Shepmaster

Reputation: 431489

You can only use generics when defining the struct, but you can use trait bounds on those generics to restrict it to specific types. Here, I've used the where clause:

trait Vertex {}

struct Mesh<R> {
    r: R,
}

struct Cube<V, R>
    where V: Vertex,
{
    vertex_data: [V; 24],
    mesh: Mesh<R>,
}

fn main() {}

You will also want to use those bounds on any method implementations:

impl<V, R> Cube<V, R>
    where V: Vertex,
{
    fn new(vertex: V, mesh: Mesh<R>) -> Cube<V, R> { ... }
}

In fact, you frequently will only see the where clause on the implementation, not the struct. This is because you normally only access the struct through the methods, and the struct is opaque to the end user. If you have public fields it may be worth leaving the bound in both places though.

Upvotes: 6

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