Trait Aggregate 

pub trait Aggregate: Default {
    type Event;
    type Error;
    type Id;

    const KIND: &'static str;

    // Required method
    fn apply(&mut self, event: &Self::Event);
}

Command-side entities that produce domain events.

Aggregates rebuild their state from events (Apply<E>) and validate commands via Handle<C>. The derive macro generates the event enum and plumbing automatically, while keeping your state struct focused on domain behaviour.

Aggregates are domain objects and do not require serialisation by default.

If you enable snapshots (via Repository::with_snapshots), the aggregate state must be serialisable (Serialize + DeserializeOwned).

Required Associated Constants

const KIND: &'static str

Aggregate type identifier used by the event store.

This is combined with the aggregate ID to create stream identifiers. Use lowercase, kebab-case for consistency: "product", "user-account", etc.

Required Associated Types

type Event

type Error

type Id

Required Methods

fn apply(&mut self, event: &Self::Event)

Apply an event to update aggregate state.

This is called during event replay to rebuild aggregate state from history.

When using #[derive(Aggregate)], this dispatches to your Apply<E> implementations. For hand-written aggregates, implement this directly with a match expression.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors