Supertraits / Trait Dependencies

Traits can be extended by new traits.

#![allow(unused)]
fn main() {
pub trait DeviceId {
    /* trait for device ID types */
}

pub trait GraphicsDevice: DeviceId {
    /* Graphics device specifics */
}

// From stdlib

pub trait Ord: PartialOrd {
    /* methods for Ord */
}
}

  • When authoring a trait, you can specify traits that a type must also. These are called Supertraits.

    For the example above, any type that implements GraphicsDevice must also implement DeviceId.

  • These hierarchies of traits let us design systems around the behavior of complex real-world taxonomies (like machine hardware, operating system specifics).

  • This is distinct from object inheritance! But it looks similar.

    • Object inheritance allows for overrides and brings in the behavior of the inherited types by default.

    • A trait having a supertrait doesn’t mean that trait can override method implementations as default implementations.

ref:

  • https://doc.rust-lang.org/reference/items/traits.html?highlight=supertrait#r-items.traits.supertraits