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设计模式--备忘录(Memento)模式

 2 years ago
source link: https://segmentfault.com/a/1190000040406651
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在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态，这样以后就可以将该对象恢复到原先保存的状态

  • 备忘录（Memento）存储原发器（Originator）对象的内部状态，在需要时恢复原发器状态
  • Memento模式的核心是信息隐藏，即Originator需要向外界隐藏信息，保持其封装性，但同时又需要将状态保持到外界（Memento）

Go语言代码实现

memento.go

package Memento

type Memento struct {
   state int
}

func NewMemento(value int) *Memento{
   return &Memento{value}
}

type Number struct {
   value int
}

func NewNumber (value int) *Number{
   return &Number{value: value}
}

func (n * Number) Double(){
   n.value = 2 * n.value
}

func (n *Number) Half () {
   n.value /= 2
}

func (n *Number) Value() int {
   return n.value
}

func (n *Number) CreateMemento() *Memento{
   return NewMemento(n.value)
}

func (n *Number) SetMemento(memento *Memento){
   n.value = memento.state
}

memento_test.go

package Memento

import (
   "fmt"
   "testing"
)

func TestNumber_SetMemento(t *testing.T) {
   n := NewNumber(7)
   n.Double()
   n.Double()
   memento := n.CreateMemento() //记录当前时刻的值
   n.Half()
   n.SetMemento(memento) //拿出当时记录的值
   fmt.Println(n.value)
}

report

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