add facade

design-patterns/facade/facade.go

@@ -0,0 +1,40 @@
+package facade
+
+import (
+	"fmt"
+	"io"
+)
+
+type OrderSystem struct {
+	out io.Writer
+}
+
+func (o *OrderSystem) Settlement() float64 {
+	fmt.Fprintf(o.out, "Settlement completed\n")
+	return 20.0
+}
+
+type PaymentSystem struct {
+	out io.Writer
+}
+
+func (p *PaymentSystem) Payment(amount float64) {
+	fmt.Fprintf(p.out, "Payment of $%.2f\n", amount)
+
+}
+
+type ShopSystem struct {
+	order   *OrderSystem
+	payment *PaymentSystem
+}
+
+func (s *ShopSystem) Buy() {
+	s.payment.Payment(s.order.Settlement())
+}
+
+func NewShopSystem(out io.Writer) *ShopSystem {
+	return &ShopSystem{
+		order:   &OrderSystem{out: out},
+		payment: &PaymentSystem{out: out},
+	}
+}

design-patterns/facade/facade_test.go

@@ -0,0 +1,15 @@
+package facade_test
+
+import (
+	"os"
+
+	"github.com/cndoit18/cs_study_plan/design-patterns/facade"
+)
+
+func ExampleNewShopSystem() {
+	shopSystem := facade.NewShopSystem(os.Stdout)
+	shopSystem.Buy()
+	// Output:
+	// Settlement completed
+	// Payment of $20.00
+}