mirror of
https://github.com/crazybber/awesome-patterns.git
synced 2024-11-28 15:56:04 +03:00
111 lines
2.5 KiB
Go
111 lines
2.5 KiB
Go
// 访问者模式 visitor pattern.
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// 该模式用于将数据结构和操作进行分离，同样用于分离操作的还有策略模式(strategy pattern)，但两者存在侧重点的不同.
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// 访问者模式侧重于扩展访问的方法类型，是为了对某一个类及其子类的访问方式进行扩展，允许增加更多不同的访问者，但不宜增加更多的Host.
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// 以下以实体A(仅有玩家、NPC、物体三类)被访问(查看信息、发起挑战等，此处可扩展)的过程
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package main
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import "log"
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// 如果这里有更多的新类型Host需要扩展，则不宜使用访问者模式
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type Host interface {
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Accept(Visitor)
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}
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type PlayerHost struct {
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Name string
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Level int
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}
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func (p PlayerHost)Accept(v Visitor){
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v.VisitPlayer(p)
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}
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type NPCHost struct {
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Name string
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IsImmortal bool
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}
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func (n NPCHost)Accept(v Visitor){
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v.VisitNPC(n)
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}
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type ObjectHost struct {
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Name string
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Price int
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}
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func (o ObjectHost)Accept(v Visitor){
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v.VisitObject(o)
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}
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type Visitor interface {
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VisitPlayer(PlayerHost)
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VisitNPC(NPCHost)
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VisitObject(ObjectHost)
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}
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// 访问者允许有不同类型的访问者
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// 仅查看信息的访问者
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type InfoVisitor struct {}
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func (InfoVisitor) VisitPlayer(p PlayerHost) {
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log.Printf("Player -> Name:%s ,Level:%d\n" ,p.Name ,p.Level)
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}
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func (InfoVisitor) VisitNPC(n NPCHost) {
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log.Printf("NPC -> Name:%s ,Immortal:%v\n" ,n.Name ,n.IsImmortal)
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}
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func (InfoVisitor) VisitObject(o ObjectHost) {
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log.Printf("Object -> Name:%s ,Price:%d\n" ,o.Name ,o.Price)
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}
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// 发起攻击的访问者
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type AggressiveVisitor struct {}
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func (AggressiveVisitor) VisitPlayer(p PlayerHost) {
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log.Printf("Attack %s\n" ,p.Name)
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}
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func (AggressiveVisitor) VisitNPC(n NPCHost) {
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log.Printf("Attack NPC %s\n" ,n.Name)
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}
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func (AggressiveVisitor) VisitObject(o ObjectHost) {
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log.Printf("Unsupported target %s\n" ,o.Name)
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}
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func main(){
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infoVst := InfoVisitor{}
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agrVst := AggressiveVisitor{}
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pA := PlayerHost{"icg" ,1}
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pB := PlayerHost{"sz" ,2}
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npc := NPCHost{"nyn" ,true}
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obj := ObjectHost{"cake" ,19}
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hostList := []Host{pA ,npc ,obj ,pB}
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for _ ,v := range hostList{
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v.Accept(infoVst)
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}
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println()
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for _ ,v := range hostList{
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v.Accept(agrVst)
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}
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/*
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output:
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2019/05/04 10:00:49 Player -> Name:icg ,Level:1
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2019/05/04 10:00:49 NPC -> Name:nyn ,Immortal:true
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2019/05/04 10:00:49 Object -> Name:cake ,Price:19
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2019/05/04 10:00:49 Player -> Name:sz ,Level:2
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2019/05/04 10:00:49 Attack icg
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2019/05/04 10:00:49 Attack NPC nyn
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2019/05/04 10:00:49 Unsupported target cake
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2019/05/04 10:00:49 Attack sz
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*/
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}
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