learning Pointer Implemetation

pimple.cpp

//==================file.h===========
#ifndef FILE_H
#define FILE_H

class file
{
public:
	file();
	file(const file& rhs);
	file& operator =(const file&);
	~file();
	
	void read(const char *file_name);
	void show();
private:
	class impl;
	impl* pimpl;
};

#endif
//===============end of file.h===========


//==================file.cpp==============
#include "file.h"
#include <iostream>
#include <vector>
#include <string>
#include <fstream>

class file::impl
{
public:
	// ファイルの読み込み
	void read(const char *file_name)
	{
		std::ifstream fin(file_name);
		std::string line;
		
		while(fin && getline(fin, line))
		{
			line_data.push_back(line);
		}
		
		fin.close();
	}
	// ファイルの表示
	void show()
	{
		std::vector<std::string>::iterator it;
		
		for(it = line_data.begin(); it != line_data.end(); it++)
		{
			std::cout << *it << std::endl;
		}
	}
private:
	std::vector<std::string> line_data;
};


file::file()
: pimpl(new file::impl()) {}

file::file(const file &rhs)
: pimpl(new file::impl(*rhs.pimpl)) {}

file::~file()
{
	delete pimpl;
}

file&
file::operator =(const file& rhs)
{
	impl *tmp = pimpl;
	pimpl = new file::impl(*rhs.pimpl);
	delete tmp;
	return *this;
}

// implの呼び出し
void
file::read(const char *file_name)
{
	pimpl->read(file_name);
}

void
file::show()
{
	pimpl->show();
}
//===============end of file.cpp==========



//==================main.cpp==============
#include "file.h"

int main()
{
  file a;
  a.read("main.cpp");
  a.show();
}
//==============end of main.cpp===========