go-fsm

An ease to use finit state machine golang implementation.Turn any struct to a fsm with graphviz visualization supported.

usage

full example

take order status as a full example https://github.com/FingerLiu/go-fsm/blob/main/example.go

or the singleton version https://github.com/FingerLiu/go-fsm/blob/main/example_singleton.go

define fsm

import (
    "context"
    "fmt"
    "github.com/FingerLiu/go-fsm/fsm"
)

func NewOrder(id int, name string, orderType OrderType) *Order {
	order := &Order{
		ID:        id,
		Name:      name,
		OrderType: orderType,
		Status:    OrderStatusCreated,
	}
	ctx := context.Background()
	orderFsm := fsm.NewFSM(ctx, name).
		// add state to fsm
		AddStates(OrderStatusCreated, OrderStatusCancelled,
			OrderStatusPaid, OrderStatusCheckout,
			OrderStatusDelivering, OrderStatusDelivered, OrderStatusFinished).
		//add transition from S to E with condition check C
		AddTransition(OrderStatusCreated, OrderStatusCancelled).
		AddTransition(OrderStatusCreated, OrderStatusPaid).
		AddTransition(OrderStatusPaid, OrderStatusCheckout).
		AddTransition(OrderStatusCheckout, OrderStatusDelivering).
		AddTransition(OrderStatusDelivering, OrderStatusDelivered).
		AddTransition(OrderStatusDelivered, OrderStatusFinished).
		//virtual order do not need deliver
		AddTransitionOn(OrderStatusCheckout, OrderStatusFinished, Order.IsVirtual).
		// add transition on a condition
		AddTransitionOn(OrderStatusPaid, OrderStatusCancelled, orderService.IsPhysical).
		// add hook for a specific state(enter/exit)
		AddStateEnterHook(OrderStatusCancelled, orderService.stopDeliver).
		// global hook is triggered when state change(enter/exit) success.
		// here we use hook to save sate to order status field in database.
		AddGlobalEnterHook(orderService.saveStatus)

	orderFsm.SetState(orderService.Status)

	orderService.fsm = orderFsm

	fmt.Printf("[order] order created %v\n", order)
	return order
}

transit

	fmt.Println("------ start transit virtual order ------")
	order := NewOrder(1, "my_first_physical_order", OrderTypePhysical)
	order.Transit(OrderStatusPaid)
	
	// this will fail because condition check not met
	// and order status will stay in paid
	order.Transit(OrderStatusCancelled)
	fmt.Printf("[order] order status is %s\n", order.GetCurrentStatus())

	fmt.Println("------ start transit physical order ------")
	
	orderVirtual := NewOrder(1, "my_first_physical_order", OrderTypeVirtual)
	orderVirtual.Transit(OrderStatusPaid)
	// this will pass
	orderVirtual.Transit(OrderStatusCancelled)
	fmt.Printf("[order] order status is %s\n", orderVirtual.GetCurrentStatus())

singleton

If you don't want instance a fsm for every object, you can use singletonfsm. A singleton fsm does not have concept of current/setState, it serves as a stateless util.

	log.Println("start singletonfsm test with order")
	orderV2Service := NewOrderV2Service()
	orderPhysical := NewOrderV2(1, "my_first_physical_order", OrderTypePhysical)
	orderVirtual := NewOrderV2(1, "my_first_physical_order", OrderTypeVirtual)

	log.Println("------ start transit physical order ------")
	ctx := context.Background()
	ctx1 := context.WithValue(ctx, "order", orderPhysical)
	orderV2Service.Transit(ctx1, orderPhysical.Status, OrderStatusPaid)
	orderV2Service.Transit(ctx1, orderPhysical.Status, OrderStatusCancelled)
	log.Printf("[order] order status is %s\n", orderPhysical.Status)

visualization

    // you can gen dot file or a png image
    order.fsm.RenderGraphvizDot()
    order.fsm.RenderGraphvizImage("./demo.png")

FingerLiu / go-fsm