go-patterns/behavioral/state.md

Strategy Pattern

Strategy behavioral design pattern allow an object alter its behavior when its internal state changes. The object will appear on change its class.

Implementation

package state
type State interface {
	executeState(c *Context)
}

type Context struct {
	StepIndex int
	StepName  string
	Current   State
}

type StartState struct{}

func (s *StartState) executeState(c *Context) {
	c.StepIndex = 1
	c.StepName = "start"
	c.Current = &StartState{}
}

type InprogressState struct{}

func (s *InprogressState) executeState(c *Context) {
	c.StepIndex = 2
	c.StepName = "inprogress"
	c.Current = &InprogressState{}
}

type StopState struct{}

func (s *StopState) executeState(c *Context) {
	c.StepIndex = 3
	c.StepName = "stop"
	c.Current = &StopState{}
}

Usage

	context := &Context{}
	var state State

	state = &StartState{}
	state.executeState(context)
	fmt.Println("state: ", context)

	state = &InprogressState{}
	state.executeState(context)
	fmt.Println("state: ", context)

	state = &StopState{}
	state.executeState(context)
	fmt.Println("state: ", context)