class AggregateRoot

Base class for implementing event-sourced aggregate roots.

Aggregate roots are the core building blocks of domain-driven design and event sourcing. They encapsulate business logic, maintain consistency boundaries, and generate events that represent state changes. The aggregate’s current state is rebuilt by replaying its historical events through reducer functions.

Key Features: - *\*Event Sourcing\**: State is derived from events, not stored directly - \**Business Logic\**: Encapsulates domain rules and invariants - \**Event Generation\**: Emits events when state changes occur - \**Immutable History\**: Complete audit trail of all changes - \**Checkpointing\*\*: Optional performance optimization for large event histories

Properties

config

Aggregate configuration settings

Signature

readonly config: AggregateConfig;

history

Complete event history for this aggregate instance

Signature

history: EventicleEvent[];

id

Unique identifier for this aggregate instance

Signature

id: string;

newEvents

Events raised since last persistence (pending events)

Signature

newEvents: EventicleEvent[];

reducers

Event reducer functions mapping event types to state update logic

Signature

reducers: any;

replaying

Flag indicating if aggregate is currently replaying historical events

Signature

replaying: boolean;

type

Signature

get type(): string;

Constructors

(constructor)(type)

Constructs a new instance of the AggregateRoot class

Parameters
Name	Type	Description
`type`	`string \| ~AggregateConfig`

Signature

constructor(type: string | AggregateConfig);

Methods

currentCheckpoint()

Returns the current state as a checkpoint for performance optimization.

Checkpoints allow aggregates with long event histories to snapshot their current state, reducing the time needed to rebuild from events. This method should be implemented when storeCheckpoint is enabled in the config.

Signature

currentCheckpoint(): object;

handleEvent(event)

Applies an event to the aggregate state using the appropriate reducer.

This method is called automatically by raiseEvent and during event replay. It looks up the reducer function for the event type and applies the event to update the aggregate’s state.

Parameters
Name	Type	Description
`event`	`EventicleEvent`	The event to apply to the aggregate state
Returns	`void`

Signature

handleEvent(event: EventicleEvent): void;

raiseEvent(event)

Raises a new domain event and applies it to the aggregate state.

This is the primary method for recording state changes in event-sourced aggregates. The event is automatically assigned metadata (ID, timestamp, source) and applied through the appropriate reducer function.

Parameters
Name	Type	Description
`event`	`EventicleEvent`	The domain event to raise
Returns	`EventicleEvent<any>`	The event with populated metadata

Signature

raiseEvent(event: EventicleEvent): EventicleEvent<any>;