Andres Osinski <[email protected]> wrote: > Hi all, I have a question which I'm sure must have already been discussed > and dealt with, but I wanted to understand the design rationale: > > A lot of trait-level functionality would be enhanced if a trait could > specify members to be included in the struct which implements the trait. > This can be solved in practice by wrapping member access in accessor > methods, but I fail to see why that would be preferable.
IMO this would completely defeat the advantage of traits over inheritance based interfaces. The beauty of traits is, that the trait and the type are separated, only connected by the implementation: - You can add an implementation for your custom trait to any existing type. - You can add an implementation for any existing trait to your custom type. Now if you add a fields specification to the trait, the former isn't true anymore. The type has now a dependency on the trait since it must at least contain a field of a given type, if not even with a given name. If you the concrete type is under your control, this is obviously not a problem, as it is the case with inheritance based interfaces. But you cannot simply assume that for every use case. Tobi _______________________________________________ Rust-dev mailing list [email protected] https://mail.mozilla.org/listinfo/rust-dev
