Chain of Responsibility Pattern

1.Chain of Responsibility模式:将可能处理一个请求的对象链接成一个链，并将请求在这个链上传递，直到有对象处理该请求（可能需要提供一个默认处理所有请求的类，例如MFC中的CwinApp类）。

2.Chain of Responsibility Pattern 结构图

3.实现

 1 #ifndef _HANDLE_H_
 2 #define _HANDLE_H_
 3
 4 class Handle
 5 {
 6 public:
 7     virtual ~Handle();
 8     virtual void HandleRequest() = 0;
 9     void SetSuccessor(Handle* succ);
10     Handle* GetSuccessor();
11
12 protected:
13     Handle();
14     Handle(Handle* succ);
15
16 private:
17     Handle* _succ;
18 };
19
20 class ConcreteHandleA:public Handle
21 {
22 public:
23     ConcreteHandleA();
24     ~ConcreteHandleA();
25     ConcreteHandleA(Handle* succ);
26     void HandleRequest();
27
28 protected:
29 private:
30 };
31
32 class ConcreteHandleB:public Handle
33 {
34 public:
35     ConcreteHandleB();
36     ~ConcreteHandleB();
37     ConcreteHandleB(Handle* succ);
38     void HandleRequest();
39 protected:
40 private:
41 };
42
43 #endif

Handle.h

 1 #include "Handle.h"
 2 #include <iostream>
 3 using namespace std;
 4
 5 Handle::Handle()
 6 {
 7     _succ = 0;
 8 }
 9 Handle::~Handle()
10 {
11     delete _succ;
12 }
13 Handle::Handle(Handle* succ)
14 {
15     this->_succ = succ;
16 }
17 void Handle::SetSuccessor(Handle* succ)
18 {
19     _succ = succ;
20 }
21 Handle* Handle::GetSuccessor()
22 {
23     return _succ;
24 }
25 void Handle::HandleRequest()
26 {
27
28 }
29 ConcreteHandleA::ConcreteHandleA()
30 {
31
32 }
33 ConcreteHandleA::ConcreteHandleA(Handle* succ):Handle(succ)
34 {
35
36 }
37 ConcreteHandleA::~ConcreteHandleA()
38 {
39
40 }
41 void ConcreteHandleA::HandleRequest()
42 {
43     if (this->GetSuccessor() != 0)
44     {
45         cout<<"ConcreteHandleA 我把处理权给后继节点....."<<endl;
46         this->GetSuccessor()->HandleRequest();
47     }
48     else
49     {
50         cout<<"ConcreteHandleA 没有后继了，我必须自己处理...."<<endl;
51     }
52 }
53 ConcreteHandleB::ConcreteHandleB()
54 {
55
56 }
57 ConcreteHandleB::ConcreteHandleB(Handle* succ):Handle(succ)
58 {
59
60 }
61 ConcreteHandleB::~ConcreteHandleB()
62 {
63
64 }
65 void ConcreteHandleB::HandleRequest()
66 {
67     if (this->GetSuccessor() != 0)
68     {
69         cout<<"ConcreteHandleB 我把处理权给后继节点....."<<endl;
70         this->GetSuccessor()->HandleRequest();
71     }
72     else
73     {
74         cout<<"ConcreteHandleB 没有后继了，我必须自己处理...."<<endl;
75     }
76 }

Handle.cpp

 1 #include "Handle.h"
 2 #include <iostream>
 3 using namespace std;
 4
 5 int main(int argc,char* argv[])
 6 {
 7     Handle* h1 = new ConcreteHandleA();
 8     Handle* h2 = new ConcreteHandleB();
 9     h1->SetSuccessor(h2);
10     h1->HandleRequest();
11     return 0;
12 }

main.cpp