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这篇文章主要讲解了“go.cqrs中AggregateRoot的用法”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“go.cqrs中AggregateRoot的用法”吧！
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本文主要研究一下go.cqrs的AggregateRoot
//AggregateRoot is the interface that all aggregates should implement
type AggregateRoot interface {
AggregateID() string
OriginalVersion() int
CurrentVersion() int
IncrementVersion()
Apply(events EventMessage, isNew bool)
TrackChange(EventMessage)
GetChanges() []EventMessage
ClearChanges()
}AggregateRoot接口定义了AggregateID、OriginalVersion、CurrentVersion、IncrementVersion、Apply、TrackChange、GetChanges、ClearChanges方法
// AggregateBase is a type that can be embedded in an AggregateRoot
// implementation to handle common aggragate behaviour
//
// All required methods to implement an aggregate are here, to implement the
// Aggregate root interface your aggregate will need to implement the Apply
// method that will contain behaviour specific to your aggregate.
type AggregateBase struct {
id string
version int
changes []EventMessage
}
// NewAggregateBase contructs a new AggregateBase.
func NewAggregateBase(id string) *AggregateBase {
return &AggregateBase{
id: id,
changes: []EventMessage{},
version: -1,
}
}
// AggregateID returns the AggregateID
func (a *AggregateBase) AggregateID() string {
return a.id
}
// OriginalVersion returns the version of the aggregate as it was when it was
// instantiated or loaded from the repository.
//
// Importantly an aggregate with one event applied will be at version 0
// this allows the aggregates to match the version in the eventstore where
// the first event will be version 0.
func (a *AggregateBase) OriginalVersion() int {
return a.version
}
// CurrentVersion returns the version of the aggregate as it was when it was
// instantiated or loaded from the repository.
//
// Importantly an aggregate with one event applied will be at version 0
// this allows the aggregates to match the version in the eventstore where
// the first event will be version 0.
func (a *AggregateBase) CurrentVersion() int {
return a.version + len(a.changes)
}
// IncrementVersion increments the aggregate version number by one.
func (a *AggregateBase) IncrementVersion() {
a.version++
}
// TrackChange stores the EventMessage in the changes collection.
//
// Changes are new, unpersisted events that have been applied to the aggregate.
func (a *AggregateBase) TrackChange(event EventMessage) {
a.changes = append(a.changes, event)
}
// GetChanges returns the collection of new unpersisted events that have
// been applied to the aggregate.
func (a *AggregateBase) GetChanges() []EventMessage {
return a.changes
}
//ClearChanges removes all unpersisted events from the aggregate.
func (a *AggregateBase) ClearChanges() {
a.changes = []EventMessage{}
}AggregateBase定义了id、version、changes属性；AggregateID方法返回id；OriginalVersion方法返回version；CurrentVersion返回version+len(a.changes)；IncrementVersion递增version；TrackChange方法往changes增加event；GetChanges方法返回changes；ClearChanges会清空changes
// EventMessage is the interface that a command must implement.
type EventMessage interface {
// AggregateID returns the ID of the Aggregate that the event relates to
AggregateID() string
// GetHeaders returns the key value collection of headers for the event.
//
// Headers are metadata about the event that do not form part of the
// actual event but are still required to be persisted alongside the event.
GetHeaders() map[string]interface{}
// SetHeader sets the value of the header specified by the key
SetHeader(string, interface{})
// Returns the actual event which is the payload of the event message.
Event() interface{}
// EventType returns a string descriptor of the command name
EventType() string
// Version returns the version of the event
Version() *int
}EventMessage接口定义了AggregateID、GetHeaders、SetHeader、Event、EventType、Version方法
// EventDescriptor is an implementation of the event message interface.
type EventDescriptor struct {
id string
event interface{}
headers map[string]interface{}
version *int
}
// NewEventMessage returns a new event descriptor
func NewEventMessage(aggregateID string, event interface{}, version *int) *EventDescriptor {
return &EventDescriptor{
id: aggregateID,
event: event,
headers: make(map[string]interface{}),
version: version,
}
}
// EventType returns the name of the event type as a string.
func (c *EventDescriptor) EventType() string {
return typeOf(c.event)
}
// AggregateID returns the ID of the Aggregate that the event relates to.
func (c *EventDescriptor) AggregateID() string {
return c.id
}
// GetHeaders returns the headers for the event.
func (c *EventDescriptor) GetHeaders() map[string]interface{} {
return c.headers
}
// SetHeader sets the value of the header specified by the key
func (c *EventDescriptor) SetHeader(key string, value interface{}) {
c.headers[key] = value
}
// Event the event payload of the event message
func (c *EventDescriptor) Event() interface{} {
return c.event
}
// Version returns the version of the event
func (c *EventDescriptor) Version() *int {
return c.version
}EventDescriptor定义了id、event、headers、version属性；其EventType返回typeOf(c.event)；AggregateID返回id；GetHeaders返回headers；SetHeader会设置header；Event方法返回event；Version返回version
go.cqrs的AggregateRoot接口定义了AggregateID、OriginalVersion、CurrentVersion、IncrementVersion、Apply、TrackChange、GetChanges、ClearChanges方法。
感谢各位的阅读，以上就是“go.cqrs中AggregateRoot的用法”的内容了，经过本文的学习后，相信大家对go.cqrs中AggregateRoot的用法这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是创新互联，小编将为大家推送更多相关知识点的文章，欢迎关注！