add bridge mode

Author: senghoo

22_bridge/README.md

@@ -0,0 +1,7 @@
+# 桥接模式
+
+桥接模式分离抽象部分和实现部分。使得两部分独立扩展。
+
+桥接模式类似于策略模式，区别在于策略模式封装一系列算法使得算法可以互相替换。
+
+策略模式使抽象部分和实现部分分离，可以独立变化。

22_bridge/bridge.go

@@ -0,0 +1,59 @@
+package bridge
+
+import "fmt"
+
+type AbstractMessage interface {
+	SendMessage(text, to string)
+}
+
+type MessageImplementer interface {
+	Send(text, to string)
+}
+
+type MessageSMS struct{}
+
+func ViaSMS() MessageImplementer {
+	return &MessageSMS{}
+}
+
+func (*MessageSMS) Send(text, to string) {
+	fmt.Printf("send %s to %s via SMS", text, to)
+}
+
+type MessageEmail struct{}
+
+func ViaEmail() MessageImplementer {
+	return &MessageEmail{}
+}
+
+func (*MessageEmail) Send(text, to string) {
+	fmt.Printf("send %s to %s via Email", text, to)
+}
+
+type CommonMessage struct {
+	method MessageImplementer
+}
+
+func NewCommonMessage(method MessageImplementer) *CommonMessage {
+	return &CommonMessage{
+		method: method,
+	}
+}
+
+func (m *CommonMessage) SendMessage(text, to string) {
+	m.method.Send(text, to)
+}
+
+type UrgencyMessage struct {
+	method MessageImplementer
+}
+
+func NewUrgencyMessage(method MessageImplementer) *UrgencyMessage {
+	return &UrgencyMessage{
+		method: method,
+	}
+}
+
+func (m *UrgencyMessage) SendMessage(text, to string) {
+	m.method.Send(fmt.Sprintf("[Urgency] %s", text), to)
+}

22_bridge/bridge_test.go

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+package bridge
+
+func ExampleCommonSMS() {
+	m := NewCommonMessage(ViaSMS())
+	m.SendMessage("have a drink?", "bob")
+	// Output:
+	// send have a drink? to bob via SMS
+}
+
+func ExampleCommonEmail() {
+	m := NewCommonMessage(ViaEmail())
+	m.SendMessage("have a drink?", "bob")
+	// Output:
+	// send have a drink? to bob via Email
+}
+
+func ExampleUrgencySMS() {
+	m := NewUrgencyMessage(ViaSMS())
+	m.SendMessage("have a drink?", "bob")
+	// Output:
+	// send [Urgency] have a drink? to bob via SMS
+}
+
+func ExampleUrgencyEmail() {
+	m := NewUrgencyMessage(ViaEmail())
+	m.SendMessage("have a drink?", "bob")
+	// Output:
+	// send [Urgency] have a drink? to bob via Email
+}