Go设计模式之中介者模式讲解和代码示例

package main
type Train interface {
	arrive()
	depart()
	permitArrival()
}

package main
import "fmt"
type PassengerTrain struct {
	mediator Mediator
}
// 火车停靠
func (pt *PassengerTrain) arrive() {
	if !pt.mediator.canArrive(pt) {
		fmt.Println("PassengerTrain: Arrival blocked, waiting")
		return
	}
	fmt.Println("PassengerTrain: arrived")
}
// 获取离开
func (pt *PassengerTrain) depart() {
	fmt.Println("PassengerTrain: leaving")
	pt.mediator.notifyAboutDeparture()
}
func (pt *PassengerTrain) permitArrival() {
	fmt.Println("PassengerTrain: Arrival permitted, arriving")
	pt.arrive()
}

package main
import "fmt"
type FreightTrain struct {
	mediator Mediator
}
func (g *FreightTrain) arrive() {
	if !g.mediator.canArrive(g) {
		fmt.Println("FreightTrain: Arrival blocked, waiting")
		return
	}
	fmt.Println("FreightTrain: arrived")
}
func (g *FreightTrain) depart() {
	fmt.Println("FreightTrain: leaving")
	g.mediator.notifyAboutDeparture()
}
func (g *FreightTrain) permitArrival() {
	fmt.Println("FreightTrain: Arrival permitted")
	g.arrive()
}

package main
type Mediator interface {
	canArrive(Train) bool
	notifyAboutDeparture()
}

package main
type StationManager struct {
	isPlatformFree bool
	trainQueue     []Train
}
func newStationManager() *StationManager {
	return &StationManager{
		isPlatformFree: true,
	}
}
func (s *StationManager) canArrive(t Train) bool {
	if s.isPlatformFree {
		s.isPlatformFree = false
		return true
	}
	s.trainQueue = append(s.trainQueue, t)
	return false
}
func (s *StationManager) notifyAboutDeparture() {
	if !s.isPlatformFree {
		s.isPlatformFree = true
	}
	if len(s.trainQueue) > 0 {
		firstTrainInQueue := s.trainQueue[0]
		s.trainQueue = s.trainQueue[1:]
		firstTrainInQueue.permitArrival()
	}
}

package main
func main() {
	stationManager := newStationManager()
	passengerTrain := &PassengerTrain{
		mediator: stationManager,
	}
	freightTrain := &FreightTrain{
		mediator: stationManager,
	}
	passengerTrain.arrive()
	freightTrain.arrive()
	passengerTrain.depart()
}