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十四、strategy 策略模式

https://refactoringguru.cn/design-patterns/strategy

需求: client 知道很多不同的策略, 希望在运行时切换.

场景示例: 就像高德地图一样, 导航到某地, 用户可选择其一: 地铁, 自驾, 打车, 自行车 等.

实现方式: 定义策略接口, 上层组合该接口. client 在运行时切换 具体策略.

14.1 map_app

├── mapapp.go
├── mapapp_test.go
└── navigate_strategy.go

14.1.1 map_app_test.go

package _41map_appimport "testing"func TestMapApp(t *testing.T) {app := MapApp{}app.SetNavigateStrategy(&WalkNavigateStrategy{})app.Run()app.SetNavigateStrategy(&SubwayNavigateStrategy{})app.Run()app.SetNavigateStrategy(&TaxiNavigateStrategy{})app.Run()
}

14.1.2 map_app.go

package _41map_appimport "fmt"type MapApp struct {navigateStrategy NavigateStrategy
}func (app *MapApp) Run() {fmt.Println("打开导航地图APP")app.navigateStrategy.Navigate()fmt.Println("关闭导航地图APP")
}func (app *MapApp) SetNavigateStrategy(s NavigateStrategy) {app.navigateStrategy = s
}

14.1.3 navigate_strategy.go

package _41map_appimport "fmt"type NavigateStrategy interface {// Navigate 导航Navigate()
}type WalkNavigateStrategy struct {
}func (s *WalkNavigateStrategy) Navigate() {fmt.Println("步行导航开始")
}type SubwayNavigateStrategy struct {
}func (s *SubwayNavigateStrategy) Navigate() {fmt.Println("地铁导航开始")
}type TaxiNavigateStrategy struct {
}func (s *TaxiNavigateStrategy) Navigate() {fmt.Println("出租车导航开始")
}