add state

16_state/README.md

@@ -0,0 +1,3 @@
+# 状态模式
+
+状态模式用于分离状态和行为。

16_state/state.go

@@ -0,0 +1,96 @@
+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{}
+}

16_state/state_test.go

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+package state
+
+func ExampleWeek() {
+	ctx := NewDayContext()
+	ctx.Today()
+	ctx.Next()
+	ctx.Today()
+	ctx.Next()
+	ctx.Today()
+	ctx.Next()
+	ctx.Today()
+	ctx.Next()
+	ctx.Today()
+	ctx.Next()
+	ctx.Today()
+	ctx.Next()
+	ctx.Today()
+	ctx.Next()
+	ctx.Today()
+	ctx.Next()
+	// Output:
+	// Sunday
+	// Monday
+	// Tuesday
+	// Wednesday
+	// Thursday
+	// Friday
+	// Saturday
+	// Sunday
+}