Traits and Generics

Traits Are Interface Types

• Define methods, fields and types that must be present in the implementation of a struct or enum

• Principal mechanism for code reuse in Rust

• Interact strongly with and enhance "generic" types (parametric polymorphism)

Defining A Trait

• Just an interface specification

• Here's a hairy version

  https://play.rust-lang.org/?gist=d0087cd38ededa59f70297615c676254

• Note the following:

  • Trait bounds
  • Associated type
  • Static (default) method
  • Use of Sized marker type
  • Use of Self
  • Clever type inference
  • Implementation of our trait for standard types

Trait Bounds vs Trait Objects

• Book example

  https://play.rust-lang.org/?gist=8aaa8fe367b1e495c0318d777bd0e83b

• A specialized version of generic_salad.add(*v) will be constructed, no argument need be passed, the whole thing will be inlined

• Note the awkwardness of working with trait objects. This code is fairly fragile

Misc Trait Things

• Traits and scope control

• Subtraits