entity.go

// Copyright (c) 2017 - The Event Horizon authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package eventhorizon

import "github.com/looplab/eventhorizon/uuid"

// Entity is an item which is identified by an ID.
//
// From http://cqrs.nu/Faq:
// "Entities or reference types are characterized by having an identity that's
// not tied to their attribute values. All attributes in an entity can change
// and it's still "the same" entity. Conversely, two entities might be
// equivalent in all their attributes, but will still be distinct".
type Entity interface {
	// EntityID returns the ID of the entity.
	EntityID() uuid.UUID
}

// Versionable is an item that has a version number,
// used by version.ReadRepo and projector.EventHandler.
type Versionable interface {
	// AggregateVersion returns the version of the item.
	AggregateVersion() int
}