When to use dynamic dispatch?

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That being said, there are also cases where you know all types that implement a trait. That's when I usually recommend using an enum, if someone asks for performance optimization tips.

In that situation, you may also store each individual type in a separate collection or sort them by type in a single collection. Those are good ways to optimize for performance, but at a cost of added complexity. As always, do not optimize too early.

The trade-offs are as follows:

  • Performance:
    1. Generics
    2. Enums
    3. Trait Objects
  • Complexity (least first):
    1. Trait Objects
    2. Enums
    3. Generics
  • Binary Size (smallest first):
    1. Trait Objects
    2. Enums
    3. Generics
  • Flexibility:
    1. Generics
    2. Enums / Trait Objects¹
  • Privacy:
    1. Trait Objects
    2. Enums
    3. Generics

¹) Enums allow calling generic methods, but require a fixed amount of types. Trait objects aren't limited to a fixed amount of implementing types, but can't call generic methods and are limited in other ways, as well. See: Object Safety

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