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Struct Components

#[derive(Component)]​

The most common path. Each named field is resolved from the ComponentProvider:

  • Arc<T> fields resolve via ctx.get::<T>().await (shared with every other consumer of T).
  • Any other field resolves via ctx.get_cloned::<T>().await (requires T: Clone).
  • A field marked #[default] is built with Default::default() instead, skipping the container entirely.
use axumstart_components::Component;
use std::sync::Arc;

#[derive(Component)]
struct Database {
    pool: Arc<DbPool>,
    #[default]
    query_count: AtomicU64,
}

This expands to a ComponentBlueprint for Database impl and an inventory registration, so it participates in register_all() automatically.

Registering trait objects — #[as_trait(Trait)]​

Add #[as_trait(Trait)] to also register the component as Arc<dyn Trait>:

trait Greeter: Send + Sync {
  fn greet(&self) -> &'static str;
}

#[derive(Component)]
#[as_trait(Greeter)]
pub struct EnglishGreeter;

impl Greeter for EnglishGreeter {
  fn greet(&self) -> &'static str { "hi" }
}

// later:
pub async fn welcome(greeter: Inject<dyn Greeter>) -> &'static str {
  greeter.greet()
}

Concrete and trait-object registrations resolve to the same underlying instance.