trait-cast 0.4.0

//! This example shows how to use the `#[derive(TraitcastableAny)]` macro to make a struct castable to multiple traits.
#![allow(clippy::undocumented_unsafe_blocks)]
#![allow(
  unsafe_code,
  reason = "The example shows off the unchecked downcast functions which require unsafe code."
)]
#![cfg_attr(feature = "min_specialization", feature(min_specialization))]
#![cfg_attr(feature = "downcast_unchecked", feature(downcast_unchecked))]
#![feature(ptr_metadata)]
use trait_cast::{TraitcastableAny, TraitcastableAnyInfra, TraitcastableAnyInfraExt};

#[derive(TraitcastableAny)]
#[traitcast_targets(Dog, Cat)]
struct HybridPet {
  name: String,
}
impl HybridPet {
  fn greet(&self) {
    println!("{}: Hi", self.name);
  }
}

impl Dog for HybridPet {
  fn bark(&self) {
    println!("{}: Woof!", self.name);
  }
}
impl Cat for HybridPet {
  fn meow(&self) {
    println!("{}: Meow!", self.name);
  }
}

trait Dog {
  fn bark(&self);
}
trait Cat {
  fn meow(&self);
}
#[cfg_attr(test, test)]
fn main() {
  // The box is technically not needed but kept for added realism
  let pet = Box::new(HybridPet {
    name: "Kokusnuss".to_string(),
  });
  pet.greet();

  let castable_pet: Box<dyn TraitcastableAny> = pet;

  let as_dog: &dyn Dog = castable_pet.downcast_ref().unwrap();
  as_dog.bark();

  let as_cat: &dyn Cat = castable_pet.downcast_ref().unwrap();
  as_cat.meow();
  #[cfg(feature = "downcast_unchecked")]
  let cast_back: &HybridPet = unsafe { castable_pet.downcast_ref_unchecked() };
  #[cfg(not(feature = "downcast_unchecked"))]
  let cast_back: &HybridPet = castable_pet.downcast_ref().unwrap();
  cast_back.greet();

  let into_cat: Box<dyn Cat> = castable_pet.downcast().unwrap();
  into_cat.meow();
}