状态模式
状态模式用于分离状态和行为。
state.go
package state
import "fmt"
type Week interface {
Today()
Next(*DayContext)
}
type DayContext struct {
today Week
}
func NewDayContext() *DayContext {
return &DayContext{
today: &Sunday{},
}
}
func (d *DayContext) Today() {
d.today.Today()
}
func (d *DayContext) Next() {
d.today.Next(d)
}
type Sunday struct{}
func (*Sunday) Today() {
fmt.Printf("Sunday\n")
}
func (*Sunday) Next(ctx *DayContext) {
ctx.today = &Monday{}
}
type Monday struct{}
func (*Monday) Today() {
fmt.Printf("Monday\n")
}
func (*Monday) Next(ctx *DayContext) {
ctx.today = &Tuesday{}
}
type Tuesday struct{}
func (*Tuesday) Today() {
fmt.Printf("Tuesday\n")
}
func (*Tuesday) Next(ctx *DayContext) {
ctx.today = &Wednesday{}
}
type Wednesday struct{}
func (*Wednesday) Today() {
fmt.Printf("Wednesday\n")
}
func (*Wednesday) Next(ctx *DayContext) {
ctx.today = &Thursday{}
}
type Thursday struct{}
func (*Thursday) Today() {
fmt.Printf("Thursday\n")
}
func (*Thursday) Next(ctx *DayContext) {
ctx.today = &Friday{}
}
type Friday struct{}
func (*Friday) Today() {
fmt.Printf("Friday\n")
}
func (*Friday) Next(ctx *DayContext) {
ctx.today = &Saturday{}
}
type Saturday struct{}
func (*Saturday) Today() {
fmt.Printf("Saturday\n")
}
func (*Saturday) Next(ctx *DayContext) {
ctx.today = &Sunday{}
}
state_test.go
package state
func ExampleWeek() {
ctx := NewDayContext()
todayAndNext := func() {
ctx.Today()
ctx.Next()
}
for i := 0; i < 8; i++ {
todayAndNext()
}
// Output:
// Sunday
// Monday
// Tuesday
// Wednesday
// Thursday
// Friday
// Saturday
// Sunday
}