Introduction

transition is a Golang state machine implementation. rely on github.com/jinzhu/gorm

GO Compatibility ?

Installation

go get github.com/theplant/qor3/transition

Usage

1. Add transition to object struct

type Order struct {
    ID        uint
    ...

    // Add transition to Order
    // type Transition struct {
    //   State           string
    //   StateChangeLogs []StateChangeLog `sql:"-"`
    // }
    transition.Transition
}

2. Define states and events

var OrderStateMachine = transition.New(&Order{})

func init() {
	// Define initial state
	OrderStateMachine.Initial("draft")

    // Define what to do when enter a state and exit a state. See Callbacks for detail.
	OrderStateMachine.State("paying").Enter(func(order interface{}, tx *gorm.DB) (err error) {
        // To get order object use 'order.(*Order)'
		// business logic here
		return
	}).Exit(func(order interface{}, tx *gorm.DB) (err error) {
        // business logic here
        return
    })

    // Define event and what to do before perform transition and after transition. See Callbacks for detail.
    OrderStateMachine.Event("checkout").To("paying").From("draft").Before(func(order interface{}, tx *gorm.DB) (err error) {
        // business logic here
        return
    }).After(func(order interface{}, tx *gorm.DB) (err error) {
        // business logic here
        return
    })

    // Different state transition for one event
    cancellEvent := OrderStateMachine.Event("cancel")
    cancellEvent.To("canceled").From("draft", "paying")  // NOTE: Must define `To` before `From`
    cancellEvent.To("canceled_after_paid").From("paid", "processed")
}

3. Transfer state

// func (sm *StateMachine) Trigger(name string, value Stater, tx *gorm.DB) error {
OrderStatemachine.Trigger("checkout", *order, db)

Callbacks

There are 2 callbacks for state.

Enter

This will be performed when entering a state. Object is not persisted and object state is not changed.

OrderStateMachine.State("paying").Enter(func(order interface{}, tx *gorm.DB) (err error) {
    // To get order object use 'order.(*Order)'
    // business logic here
    return
})

Exit

This will be performed when exiting a state. Object is not persisted and object state is not changed.

OrderStateMachine.State("paying").Exit(func(order interface{}, tx *gorm.DB) (err error) {
    // business logic here
    return
})

And 2 callbacks for event.

Before

This will be performed before the event performed. Object is not persisted and object state is not changed.

OrderStateMachine.Event("checkout").From("draft").To("paying").Before(func(order interface{}, tx *gorm.DB) (err error) {
    // business logic here
    return
})

After

This will be performed after the event performed. Object is persisted.

OrderStateMachine.Event("checkout").From("draft").To("paying").Before(func(order interface{}, tx *gorm.DB) (err error) {
    // business logic here
    return
})

Features

State change log

not implemented

Copyright

Copyright © The Plant