Aggregator (simplesource-command-api 0.2.8 API)

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	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