Trait Handler 

pub trait Handler<P: 'static>: Sync + Send {
    // Required methods
    fn handle<'a>(
        &'a self,
        projection: &'a mut P,
        event: &'a Event,
    ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'a>>;
    fn aggregator_type(&self) -> &'static str;
    fn event_name(&self) -> &'static str;
}

Trait for event handlers.

Handlers process events in two modes:

• handle: For subscriptions that perform side effects (send emails, update read models)
• apply: For loading aggregate state by replaying events

This trait is typically implemented via the #[evento::handler] macro.

Required Methods

fn handle<'a>( &'a self, projection: &'a mut P, event: &'a Event, ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'a>>

Applies an event to build projection state.

This is called when loading aggregate state by replaying events. It should be a pure function that modifies the projection without side effects.

fn aggregator_type(&self) -> &'static str

Returns the aggregator type this handler processes.

fn event_name(&self) -> &'static str

Returns the event name this handler processes.

Implementors