一文详解Go语言中的有限状态机FSM

go get github.com/looplab/fsm@v1.0.1

package main

import (
	"context"
	"fmt"

	"github.com/looplab/fsm"
)

type Door struct {
	Name  string
	FSM *fsm.FSM
}

func NewDoor(name string) *Door {
	d := &Door{
		Name: name,
	}

	d.FSM = fsm.NewFSM(
		"closed",
		fsm.Events{
			{Name: "open", Src: []string{"closed"}, Dst: "open"},
			{Name: "close", Src: []string{"open"}, Dst: "closed"},
		},
		fsm.Callbacks{
			"enter_state": func(_ context.Context, e *fsm.Event) { d.enterState(e) },
		},
	)

	return d
}

func (d *Door) enterState(e *fsm.Event) {
	fmt.Printf("The door's name:%s , current state:%s\n", d.Name, e.Dst)
}

func main() {
	door := NewDoor("测试")

	fmt.Printf("fsm current state: %s \n", door.FSM.Current())

	err := door.FSM.Event(context.Background(), "open")
	if err != nil {
		fmt.Println(err)
	}
	fmt.Printf("fsm current state: %s \n", door.FSM.Current())

	err = door.FSM.Event(context.Background(), "close")
	if err != nil {
		fmt.Println(err)
	}
	fmt.Printf("fsm current state: %s \n", door.FSM.Current())
}

// NewFSM constructs a FSM from events and callbacks.
//
// The events and transitions are specified as a slice of Event structs
// specified as Events. Each Event is mapped to one or more internal
// transitions from Event.Src to Event.Dst.
// Callbacks are added as a map specified as Callbacks where the key is parsed
// as the callback event as follows, and called in the same order:
//
// 1. before_<EVENT> - called before event named <EVENT>
//
// 2. before_event - called before all events
//
// 3. leave_<OLD_STATE> - called before leaving <OLD_STATE>
//
// 4. leave_state - called before leaving all states
//
// 5. enter_<NEW_STATE> - called after entering <NEW_STATE>
//
// 6. enter_state - called after entering all states
//
// 7. after_<EVENT> - called after event named <EVENT>
//
// 8. after_event - called after all events
//
// There are also two short form versions for the most commonly used callbacks.
// They are simply the name of the event or state:
//
// 1. <NEW_STATE> - called after entering <NEW_STATE>
//
// 2. <EVENT> - called after event named <EVENT>
//
// If both a shorthand version and a full version is specified it is undefined
// which version of the callback will end up in the internal map. This is due
// to the pseudo random nature of Go maps. No checking for multiple keys is
// currently performed.

package main

import (
	"context"
	"fmt"

	"github.com/looplab/fsm"
)

type Door struct {
	Name  string
	FSM *fsm.FSM
}

func NewDoor(name string) *Door {
	d := &Door{
		Name: name,
	}

	d.FSM = fsm.NewFSM(
		"closed",
		fsm.Events{
			{Name: "open", Src: []string{"closed"}, Dst: "open"},
			{Name: "close", Src: []string{"open"}, Dst: "closed"},
		},
		fsm.Callbacks{
			"before_open": func(_ context.Context, e *fsm.Event) { d.beforeOpen(e) },
			"before_event": func(_ context.Context, e *fsm.Event) { d.beforeEvent(e) },
			"leave_closed": func(_ context.Context, e *fsm.Event) { d.leaveClosed(e) },
			"leave_state": func(_ context.Context, e *fsm.Event) { d.leaveState(e) },
			"enter_open": func(_ context.Context, e *fsm.Event) { d.enterOpen(e) },
			"enter_state": func(_ context.Context, e *fsm.Event) { d.enterState(e) },
			"after_open": func(_ context.Context, e *fsm.Event) { d.afterOpen(e) },
			"after_event": func(_ context.Context, e *fsm.Event) { d.afterEvent(e) },
		},
	)

	return d
}

func (d *Door) beforeOpen(e *fsm.Event) {
	fmt.Printf("beforeOpen, current state:%s, Dst:%s \n", d.FSM.Current(), e.Dst)
}

func (d *Door) beforeEvent(e *fsm.Event) {
	fmt.Printf("beforeEvent, current state:%s, Dst:%s \n", d.FSM.Current(), e.Dst)
}

func (d *Door) leaveClosed(e *fsm.Event) {
	fmt.Printf("leaveClosed, current state:%s, Dst:%s \n", d.FSM.Current(), e.Dst)
}

func (d *Door) leaveState(e *fsm.Event) {
	fmt.Printf("leaveState, current state:%s, Dst:%s \n", d.FSM.Current(), e.Dst)
}


func (d *Door) enterOpen(e *fsm.Event) {
	fmt.Printf("enterOpen, current state:%s, Dst:%s \n", d.FSM.Current(), e.Dst)
}


func (d *Door) enterState(e *fsm.Event) {
	fmt.Printf("enterState, current state:%s, Dst:%s \n", d.FSM.Current(), e.Dst)
}


func (d *Door) afterOpen(e *fsm.Event) {
	fmt.Printf("afterOpen, current state:%s, Dst:%s \n", d.FSM.Current(), e.Dst)
}

func (d *Door) afterEvent(e *fsm.Event) {
	fmt.Printf("afterEvent, current state:%s, Dst:%s \n", d.FSM.Current(), e.Dst)
}



func main() {
	door := NewDoor("测试")

	fmt.Printf("fsm current state: %s \n", door.FSM.Current())

	err := door.FSM.Event(context.Background(), "open")
	if err != nil {
		fmt.Println(err)
	}
	fmt.Printf("fsm current state: %s \n", door.FSM.Current())

	err = door.FSM.Event(context.Background(), "close")
	if err != nil {
		fmt.Println(err)
	}
	fmt.Printf("fsm current state: %s \n", door.FSM.Current())
}