Struct ProjectionBuilder 

pub struct ProjectionBuilder<'a, S, P>
where
    S: EventStore,
    P: Projection<Id = S::Id>,
{ /* private fields */ }

Builder used to configure which events should be loaded for a projection.

Implementations

impl<'a, S, P> ProjectionBuilder<'a, S, P>

where S: EventStore, P: Projection<Id = S::Id>,

pub fn event<E>(self) -> Self

where E: DomainEvent, P: ApplyProjection<E>, S::Metadata: Clone + Into<P::Metadata>,

Register a specific event type to load from all aggregates.

Type Constraints

The store’s metadata type must be convertible to the projection’s metadata type. Clone is required because event handlers receive metadata by reference, but Into::into() requires ownership. The metadata is cloned once per event.

Example

builder.event::<ProductRestocked>()  // All products

pub fn events<E>(self) -> Self

where E: ProjectionEvent, P: ApplyProjection<E>, S::Metadata: Clone + Into<P::Metadata>,

Register all event kinds supported by a ProjectionEvent sum type across all aggregates.

This is primarily intended for subscribing to an aggregate’s generated event enum (A::Event from #[derive(Aggregate)]) as a single “unit”, rather than registering each DomainEvent type individually.

Example

builder.events::<AccountEvent>() // All accounts, all account event variants

pub fn event_for<A, E>(self, aggregate_id: &S::Id) -> Self

where A: Aggregate<Id = S::Id>, E: DomainEvent, P: ApplyProjection<E>, S::Metadata: Clone + Into<P::Metadata>,

Register a specific event type to load from a specific aggregate instance.

Use this when you only care about a single event kind. If you want to subscribe to an aggregate’s full event enum (A::Event), prefer ProjectionBuilder::events_for.

Example

builder.event_for::<Account, FundsDeposited>(&account_id); // One account stream

pub fn events_for<A>(self, aggregate_id: &S::Id) -> Self

where A: Aggregate<Id = S::Id>, A::Event: ProjectionEvent, P: ApplyProjection<A::Event>, S::Metadata: Clone + Into<P::Metadata>,

Register all event kinds for a specific aggregate instance.

This subscribes the projection to the aggregate’s event sum type (A::Event) and loads all events in that stream that correspond to A::Event::EVENT_KINDS.

Example

let history = repository
    .build_projection::<AccountHistory>()
    .events_for::<Account>(&account_id)
    .load()?;

pub async fn load( self, ) -> Result<P, ProjectionError<S::Error, <S::Codec as Codec>::Error>>

Replays the configured events and materializes the projection.

Events are dispatched to the projection via the registered handlers, which deserialize and apply each event through the appropriate ApplyProjection implementation.

Errors

Returns ProjectionError when the store fails to load events or when an event cannot be deserialized.