Trait SingletonStore

Source

pub trait SingletonStore:
    Send
    + Sync
    + 'static {
    // Required method
    fn len(&self) -> usize;

    // Provided methods
    fn is_empty(&self) -> bool { ... }
    fn validate(&self) -> Result<(), String> { ... }
}

Expand description

Trait for generated typed singleton stores.

The #[derive(Injectable)] macro contributes to a single generated store struct that has one OnceCell<Arc<T>> per singleton-scoped injectable type.

§Design Rationale

Traditional DI containers use HashMap<TypeId, Box<dyn Any>> which requires:

Runtime type lookup
Dynamic downcasting with Any::downcast_ref
Loss of compiler guarantees

Our generated store uses named fields with concrete types:

pub struct AppSingletonStore {
    database: OnceCell<Arc<Database>>,
    cache: OnceCell<Arc<Cache>>,
}

impl AppSingletonStore {
    pub async fn database(&self, ctx: &ResolveContext) -> Arc<Database> { ... }
    pub async fn cache(&self, ctx: &ResolveContext) -> Arc<Cache> { ... }
}

This is completely typed, zero-cost, and requires no Any or TypeId.