Trait Extension 

pub trait Extension {
    // Required method
    fn register(self, app: App) -> App;
}

Spec §6: capabilities register through one seam. An extension receives the builder and returns it — providers, routes, middleware, anything.

Required Methods

fn register(self, app: App) -> App

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors