1 #include<string>
2 #include<iostream>
3 #include<set>
4 class Folder;
5 class Message;
6
7 class Folder
8 {
9 public:
10 void delete_mess(Message* pmess)
11 {
12 messages.erase(pmess);
13 }
14 void add_mess(Message* pmess)
15 {
16 messages.insert(pmess);
17 }
18 ~Folder(); // 在这里定义函数会说message类没定义。要放在外面。
19 /* {
20 // 对于每个message 要删除指向他的folder
21 for(std::set<Message*>::iterator it = messages.begin(); it != messages.end(); ++it)
22 (*it)->delete_folder(this);
23 std::cout << "~Folder" << std::endl;
24 }*/
25
26 private:
27 std::set<Message*> messages;
28 };
29
30
31 class Message
32 {
33 public:
34 Message(std::string str = ""):contents(str){}
35 Message(const Message& mes);
36 Message& operator=(const Message& mes);
37 ~Message();
38 void add_folder(Folder& fo)
39 { folders.insert(&fo);fo.add_mess(this);}
40 void delete_folder(Folder* fo)
41 { folders.erase(fo); (*fo).delete_mess(this);}
42 private:
43 std::string contents;
44 std::set<Folder*> folders;
45 };
46
47
48 Message::Message(const Message& mes):contents(mes.contents),folders(mes.folders)
49 {
50
51 for(std::set<Folder*>::iterator it = folders.begin(); it != folders.end(); ++it)
52 (*it)->add_mess(this);
53 }
54
55
56 Message& Message::operator=(const Message& mes)
57 {
58 if(this == &mes) return *this;
59 contents = mes.contents;
60 for(std::set<Folder*>::iterator it = folders.begin(); it != folders.end(); ++it)
61 (*it)->delete_mess(this);
62
63 folders = mes.folders;
64 for(std::set<Folder*>::iterator it = folders.begin(); it != folders.end(); ++it)
65 (*it)->add_mess(this);
66 return *this;
67 }
68
69 Message::~Message()
70 {
71 // 对于每一个folder要删除 每一个 folder 指向自己的信息
72 for(std::set<Folder*>::iterator it = folders.begin(); it != folders.end(); ++it)
73 (*it)->delete_mess(this);
74 std::cout<< contents << std::endl;
75 }
76
77 Folder::~Folder() // 缺少析构函数会导致：如果message删除了，则Folder里面指向垃圾对象，内存报错
78 {
79 // 对于每个message 要删除指向他的folder
80 for(std::set<Message*>::iterator it = messages.begin(); it != messages.end();)
81 {
82 std::set<Message*>::iterator next = it;
83 ++next;
84 (*it)->delete_folder(this);
85 it = next;
86 }
87 std::cout << "~Folder" << std::endl;
88 }
89
90 /*Folder::~Folder() // 这样为啥是错的。 迭代器失效的操作造成。
91 {
92 // 对于每个message 要删除指向他的folder
93 for(std::set<Message*>::iterator it = messages.begin(); it != messages.end(); ++it)
94 {
95 (*it)->delete_folder(this);
96 }
97 std::cout << "~Folder" << std::endl;
98 }
99 */
100
101 int main()
102 {
103 std::string s1("contents1");
104 std::string s2("contents2");
105
106 Message m1(s1); //栈区里面定义对象的先后
107 Message m2(s2); //顺序会影响程序的执行;特别是
108 Folder f1; // Message、Folder的类定义是交叉的。
109 Folder f2;
110
111 m2.add_folder(f2);
112 m1.add_folder(f1);
113 return 0;
114 }
