C++ Primer 练习13.4

h

#ifndef	TEST_H
#define	TEST_H

#include <set>
using namespace std;

class Folder;
class Message {
	friend class Folder;
	friend void swap(Message&, Message&);
public:
	explicit Message(const string& str = "") :
		contents(str) {}
	Message(const Message&);
	Message& operator=(const Message&);
	~Message();

	void save(Folder&);
	void remove(Folder&);
	void addfol(Folder*);
	void remfol(Folder*);
	void print();

	void test();
private:
	string contents;
	set<Folder*> folders;

	void add_to_Folders(const Message&);
	void remove_from_Folders();
};

class Folder {
	friend class Message;
	friend void swap(Message&, Message&);
public:
	Folder() = default;
	Folder(const Folder& f);
	Folder& operator=(const Folder&);
	~Folder();

	void addMsg(Message*);
	void remMsg(Message*);
	void print();

private:
	set<Message*> messages;

	void add_to_Messages(const Folder&);
	void remove_from_Messages();
};

#endif

cpp

#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include"test.h"
using namespace std;

//函数定义
void swap(Message& lhs, Message& rhs)
{
	using std::swap;
	//移除保存双方的Folder的记录
	for (auto f : lhs.folders)
		f->remMsg(&lhs);
	for (auto f : lhs.folders)
		f->remMsg(&rhs);

	swap(lhs.folders, rhs.folders);
	swap(lhs.contents, rhs.contents);

	for (auto f : lhs.folders)
		f->addMsg(&lhs);
	for (auto f : rhs.folders)
		f->addMsg(&rhs);
}

void Folder::print()
{
	cout << "Messages:";
	for (auto m : messages)
	{
		cout << " " << m->contents;
	}
	cout << endl;
}

void Message::print()
{
	cout << "Save in " << folders.size() << " Folders" << endl;
}

void Message::test()
{
	Folder f1;
	folders.insert(&f1);
}

//Message定义
Message::Message(const Message& m) :
	contents(m.contents), folders(m.folders)
{
	add_to_Folders(m);
}

Message& Message::operator=(const Message& rhs)
{
	remove_from_Folders();
	contents = rhs.contents;
	folders = rhs.folders;
	add_to_Folders(rhs);
	return *this;
}

Message::~Message()
{
	remove_from_Folders();
}

void Message::save(Folder& f)	//保存到指定Folder中
{
	addfol(&f);	//更新自身的Folders目录
	f.addMsg(this);	//向Folder中添加自身
}

void Message::remove(Folder& f)	//从指定Folder中移除
{
	remfol(&f);
	f.remMsg(this);
}

void Message::addfol(Folder* f)
{
	folders.insert(f);
}

void Message::remfol(Folder* f)
{
	folders.erase(f);
}

void Message::add_to_Folders(const Message& m)	//拷贝构造以及拷贝赋值中均需此操作
{
	for (auto f : m.folders)	//对于每个保存m的Folder
		f->addMsg(this);	//向其中添加Message自身
}

void Message::remove_from_Folders()	//清空保存自身的Folders
{
	for (auto f : folders)
		f->remMsg(this);
}

//Folder定义
Folder::Folder(const Folder& f) :
	messages(f.messages)
{
	add_to_Messages(f);
}

Folder& Folder::operator=(const Folder& f)
{
	remove_from_Messages();
	messages = f.messages;
	add_to_Messages(f);
	return *this;
}

Folder::~Folder()
{
	remove_from_Messages();
}

void Folder::addMsg(Message* m)	//添加单个Message元素
{
	messages.insert(m);
}

void Folder::remMsg(Message* m)	//同上
{
	messages.erase(m);
}

void Folder::add_to_Messages(const Folder& f)
{
	for (auto m : f.messages)	//对于目录中的每一条Message进行单次操作
		m->addfol(this);	//此处切勿使用save！因为会被save中的f.addMsg(this)循环调用自身
	//下方remove同理
}

void Folder::remove_from_Messages()	//清空目录中保存的Message
{
	for (auto m : messages)
		m->remfol(this);
}

int main()
{
	Message m1("Hello");
	Message m2("World");
	Folder f1;
	m1.save(f1);
	m2.save(f1);
	f1.print();
	m1.print();
	return 0;
}