chain of responsibility

Author: senghoo

Diff for: 21_chain_of_responsibility/README.md

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+# 职责链模式
+
+职责链模式用于分离不同职责，并且动态组合相关职责。
+
+Golang实现职责链模式时候，因为没有继承的支持，使用链对象包涵职责的方式，即：
+
+* 链对象包含当前职责对象以及下一个职责链。
+* 职责对象提供接口表示是否能处理对应请求。
+* 职责对象提供处理函数处理相关职责。
+
+同时可在职责链类中实现职责接口相关函数，使职责链对象可以当做一般职责对象是用。

Diff for: 21_chain_of_responsibility/chain.go

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+package chain
+
+import "fmt"
+
+type Manager interface {
+	HaveRight(money int) bool
+	HandleFeeRequest(name string, money int) bool
+}
+
+type RequestChain struct {
+	Manager
+	successor *RequestChain
+}
+
+func (r *RequestChain) SetSuccessor(m *RequestChain) {
+	r.successor = m
+}
+
+func (r *RequestChain) HandleFeeRequest(name string, money int) bool {
+	if r.Manager.HaveRight(money) {
+		return r.Manager.HandleFeeRequest(name, money)
+	}
+	if r.successor != nil {
+		return r.successor.HandleFeeRequest(name, money)
+	}
+	return false
+}
+
+func (r *RequestChain) HaveRight(money int) bool {
+	return true
+}
+
+type ProjectManager struct{}
+
+func NewProjectManagerChain() *RequestChain {
+	return &RequestChain{
+		Manager: &ProjectManager{},
+	}
+}
+
+func (*ProjectManager) HaveRight(money int) bool {
+	return money < 500
+}
+
+func (*ProjectManager) HandleFeeRequest(name string, money int) bool {
+	if name == "bob" {
+		fmt.Printf("Project manager permit %s %d fee request\n", name, money)
+		return true
+	}
+	fmt.Printf("Project manager don't permit %s %d fee request\n", name, money)
+	return false
+}
+
+type DepManager struct{}
+
+func NewDepManagerChain() *RequestChain {
+	return &RequestChain{
+		Manager: &DepManager{},
+	}
+}
+
+func (*DepManager) HaveRight(money int) bool {
+	return money < 5000
+}
+
+func (*DepManager) HandleFeeRequest(name string, money int) bool {
+	if name == "tom" {
+		fmt.Printf("Dep manager permit %s %d fee request\n", name, money)
+		return true
+	}
+	fmt.Printf("Dep manager don't permit %s %d fee request\n", name, money)
+	return false
+}
+
+type GeneralManager struct{}
+
+func NewGeneralManagerChain() *RequestChain {
+	return &RequestChain{
+		Manager: &GeneralManager{},
+	}
+}
+
+func (*GeneralManager) HaveRight(money int) bool {
+	return true
+}
+
+func (*GeneralManager) HandleFeeRequest(name string, money int) bool {
+	if name == "ada" {
+		fmt.Printf("General manager permit %s %d fee request\n", name, money)
+		return true
+	}
+	fmt.Printf("General manager don't permit %s %d fee request\n", name, money)
+	return false
+}

Diff for: 21_chain_of_responsibility/chain_test.go

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+package chain
+
+func ExampleChain() {
+	c1 := NewProjectManagerChain()
+	c2 := NewDepManagerChain()
+	c3 := NewGeneralManagerChain()
+
+	c1.SetSuccessor(c2)
+	c2.SetSuccessor(c3)
+
+	var c Manager = c1
+
+	c.HandleFeeRequest("bob", 400)
+	c.HandleFeeRequest("tom", 1400)
+	c.HandleFeeRequest("ada", 10000)
+	c.HandleFeeRequest("floar", 400)
+	// Output:
+	// Project manager permit bob 400 fee request
+	// Dep manager permit tom 1400 fee request
+	// General manager permit ada 10000 fee request
+	// Project manager don't permit floar 400 fee request
+
+}