io.simplesource.api

Interface Aggregator<E,A>

Type Parameters:

E - all events generated for this aggregate

A - the aggregate type

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface Aggregator<E,A>

An Aggregator is a function that builds up an aggregate from a stream of events (effectively a fold function). In Simple Sourcing, an Aggregate has one primary Aggregator that is guaranteed to be up-to-date with all events prior to executing a command against the aggregate.

Method Summary

Modifier and Type	Method and Description
A	applyEvent(A currentAggregate, E event) A function that takes the current aggregate value, the latest event and generates a new aggregate value.

Method Detail

applyEvent

A applyEvent(A currentAggregate,
             E event)

A function that takes the current aggregate value, the latest event and generates a new aggregate value. If no Aggregate exists, the InitialValue is used to create the starting value.

Parameters:

currentAggregate - the current aggregate value for this aggregate

event - the latest event to apply to this aggregate

Returns:

the updated aggregate value for this aggregate after the given event has been applied