Large App Organization

Module structure

src/
├── main.rs
├── config.rs          (#[injectable] AppConfig)
├── db/
│   ├── mod.rs
│   ├── pool.rs        (make_db_pool #[injectable(factory)])
│   └── migrations.rs
├── services/
│   ├── auth.rs        (#[injectable] AuthService)
│   ├── users.rs       (#[injectable] UserService)
│   └── orders.rs      (#[injectable] OrderService)
└── api/
    ├── mod.rs
    └── handlers.rs    (Axum handlers)

Services depend on each other

// services/auth.rs
#[injectable]
pub struct AuthService {
    #[injectable(inject(use_factory_async = crate::db::pool::make_db_pool))]
    pool: Pool<Sqlite>,
}

// services/users.rs
#[injectable]
pub struct UserService {
    #[injectable(inject(use_factory_async = crate::db::pool::make_db_pool))]
    pool: Pool<Sqlite>,
    #[injectable(inject)]
    auth: Arc<AuthService>,         // depends on AuthService
}

// services/orders.rs
#[injectable]
pub struct OrderService {
    #[injectable(inject)]
    users: Arc<UserService>,        // depends on UserService
    #[injectable(inject)]
    auth:  Arc<AuthService>,
}

main.rs assembly

mod config; mod db; mod services; mod api;

#[tokio::main]
async fn main() {
    let container = Container::builder()
        .build().await.expect("DI container failed");

    // Warm up all singletons eagerly
    let ctx = container.context();
    ctx.extract::<Inject<services::auth::AuthService>>().await.expect("AuthService");
    ctx.extract::<Inject<services::users::UserService>>().await.expect("UserService");
    ctx.extract::<Inject<services::orders::OrderService>>().await.expect("OrderService");

    let state = AxumState::new(container);
    let app = api::router(state);
    axum::serve(listener, app).await.unwrap();
}

Multi-crate workspace

# Cargo.toml (workspace)
[workspace]
members = ["app", "domain", "infra"]

Types in domain crate implement #[injectable], types in infra crate register external types via DynProvider. The app crate builds the container and wires everything together.

See guides/15-large-app-organization.md.