访问者模式

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概述

访问者模式.jpg

Golang实现

target.go

type Target interface { Accept(Visitor) }

visitor.go

type Visitor interface { VisitBuilding(building Building) VisitApartment(apartment Apartment) }

apartment.go

type Apartment struct { Name string } func (a Apartment) Accept(v Visitor) { v.VisitApartment(a) }

building.go

type Building struct { Apartments list.List } func (b Building) Accept(v Visitor) { v.VisitBuilding(b) }

cleaner.go

type Cleaner struct {} func (c Cleaner) VisitApartment(a Apartment) { fmt.Printf("cleanup Apartment %s\n", a.Name) } func (c Cleaner) VisitBuilding(b Building) { for e := b.Apartments.Front(); e != nil; e = e.Next() { c.VisitApartment(e.Value.(Apartment)) } }

viruskiller.go

type VirusKiller struct {} func (vk VirusKiller) VisitApartment(a Apartment) { fmt.Printf("Kill virus for Apartment %s\n", a.Name) } func (vk VirusKiller) VisitBuilding(b Building) { for e := b.Apartments.Front(); e != nil; e = e.Next() { vk.VisitApartment(e.Value.(Apartment)) } }

visit.go

func main() { list:= list.List{} list.PushBack(visitor.Apartment{Name:"B101"}) list.PushBack(visitor.Apartment{Name:"B102"}) list.PushBack(visitor.Apartment{Name:"B103"}) targets := []visitor.Target{ visitor.Apartment{Name:"101"}, visitor.Apartment{Name:"103"}, visitor.Building{Apartments: list}, visitor.Apartment{Name:"201"}, } c := visitor.Cleaner{} k := visitor.VirusKiller{} for _, item := range targets { item.Accept(c) } for _, item := range targets { item.Accept(k) } }

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