memento pattern

README.md

@@ -39,7 +39,7 @@ A curated collection of idiomatic design & application patterns for Go language.
 | [Chain of Responsibility](/behavioral/chain_of_responsibility/main.go) | Avoids coupling a sender to receiver by giving more than object a chance to handle the request | ✔ |
 | [Command](/behavioral/command/main.go) | Bundles a command and arguments to call later | ✔ |
 | [Mediator](/behavioral/mediator/main.go) | Connects objects and acts as a proxy | ✔ |
-| [Memento](/behavioral/memento.md) | Generate an opaque token that can be used to go back to a previous state | ✘ |
+| [Memento](/behavioral/memento/main.go) | Generate an opaque token that can be used to go back to a previous state | ✔ |
 | [Observer](/behavioral/observer.md) | Provide a callback for notification of events/changes to data | ✔ |
 | [Registry](/behavioral/registry.md) | Keep track of all subclasses of a given class | ✘ |
 | [State](/behavioral/state.md) | Encapsulates varying behavior for the same object based on its internal state | ✘ |

behavioral/mediator/main.go

@@ -1,8 +1,8 @@
 // 中介者模式(mediator pattern)
-// 当两个对象存在复杂的依赖关系时，考虑增加一个中介者使之解耦，使他们不需要进行显示的引用.
+// 当两个对象存在复杂的依赖关系时，考虑增加一个中介者使之解耦，使他们不需要进行显式的引用.
 // 但问题在于中介本身会去实现复杂的逻辑，进而导致中介者变得复杂臃肿难以维护.
 //
-// 这里是竞价和消息交换的例子.
+// 这里是竞价的例子.
 // 参与竞价的玩家只需要向中介出价就可以知道是否能买到商品，由中介确定谁的出价高
 package main
 

behavioral/memento/main.go

@@ -0,0 +1,78 @@
+// 备忘录模式 memento pattern
+// 在不影响原结构封装的情况下，能够暂时保存一个结构的状态，并能够恢复
+// 这里是一个游戏存档的例子，尝试保存玩家当前位置，并在读档的时候恢复
+package main
+
+import (
+	"container/list"
+	"log"
+)
+
+type Player struct {
+	X,Y int
+	Name string
+	// other info
+}
+
+func (p *Player)MoveTo(x,y int){
+	p.X = x
+	p.Y = y
+}
+
+func (p Player)Save()PlayerMemento{
+	return PlayerMemento{
+		X:p.X,
+		Y:p.Y,
+	}
+}
+
+func (p *Player)Restore(m PlayerMemento){
+	p.X = m.X
+	p.Y = m.Y
+}
+
+type PlayerMemento struct {
+	X,Y int
+}
+
+type PlayerCareTaker struct {
+	MementoList *list.List
+}
+
+func (ct *PlayerCareTaker)AddMemento(memento PlayerMemento){
+	ct.MementoList.PushFront(memento)
+}
+
+func (ct *PlayerCareTaker)RemoveLast()PlayerMemento{
+	ele := ct.MementoList.Front()
+	val := ct.MementoList.Remove(ele)
+	if memento ,ok := val.(PlayerMemento);ok{
+		return memento
+	}else{
+		return PlayerMemento{}
+	}
+}
+
+func main(){
+	ct := &PlayerCareTaker{list.New()}
+	icg := &Player{
+		X:114,
+		Y:514,
+		Name:"icg",
+	}
+	ct.AddMemento(icg.Save())
+	log.Println(icg.X ,icg.Y)
+
+	icg.MoveTo(810 ,19)
+	log.Println(icg.X ,icg.Y)
+	ct.AddMemento(icg.Save())
+
+	icg.MoveTo(0 ,0)
+	log.Println(icg.X ,icg.Y)
+
+	icg.Restore(ct.RemoveLast())
+	log.Println(icg.X ,icg.Y)
+
+	icg.Restore(ct.RemoveLast())
+	log.Println(icg.X ,icg.Y)
+}