模式特点：定义算法家族并且分别封装，它们之间可以相互替换而不影响客户端，客户只知道一个类就可以了。 程序实例：商场促销。
package mainimport ( "fmt")type CashSuper interface { AcceptCash(price float64) float64}//正常type CashNormal struct {}func (this *CashNormal) AcceptCash(price float64) float64 { if price < 0 { panic("不允许负数作为参数") } return price}type CashRebate struct { condition float64 rebate float64}// 满减func (this *CashRebate) AcceptCash(price float64) float64 { if price < 0 || this.condition < 0 || this.rebate < 0 { panic("不允许负数作为参数") } if price >= this.condition { return price - float64(int(price/this.condition))*this.rebate } else { return price }}type CashDiscount struct { discount float64}// 折扣func (this *CashDiscount) AcceptCash(price float64) float64 { if price < 0 || this.discount < 0 { panic("不允许负数作为参数") } if this.discount >= 1 { panic("折扣无效") } return price * this.discount}type CashContext struct { cs CashSuper}func (this *CashContext) GetResult(price float64) float64 { return this.cs.AcceptCash(price)}func NewCashContext(style string) *CashContext { context := &CashContext{} switch style { case "正常收费": context.cs = &CashNormal{} case "满300返100": context.cs = &CashRebate{300, 100} case "8折": context.cs = &CashDiscount{0.8} default: panic("计价方式错误！") } return context}func main() { var total float64 cash1 := NewCashContext("正常收费") total += cash1.GetResult(1 * 10000) cash2 := NewCashContext("满300返100") total += cash2.GetResult(1 * 10000) cash3 := NewCashContext("8折") total += cash3.GetResult(1 * 10000) fmt.Println("total:", total)}