C++Primer Plus对象和类的简单实现（）private:public:的合理使用-优快云博客

stock00.h文件实现了，类和私有变量，私有函数（类的内部使用，外部不可见），共有函数的申明（void acquire(),void buy(),void sell,void update(),void show()）.
下面通过某上市公司股票（Stock类）的买卖做案列，分析下面程序
1，Private:申明私有变量和函数的申明
2.public:申明公有函数和变量（本案例没有公用变量）

#pragma once
//stock00.h -- stock class interface 
//version 00
#ifndef STOCK00_H_
#define STOCK00_H_

#include<string>	
class Stock //class 类的申明
{
private://私有成员和函数的申明
	std::string company; //公司名称
	long shares;//所持股票的数量
	double share_val;//每股价格
	double total_val;//股票总值
	void set_tot()//内联函数，和inline同理，定义位于类申明中的函数自动成为内联韩式
	{
		total_val = shares * share_val;
	}
public://公共函数的申明

	void acquire(const std::string& co, long n, double pr);
	void buy(long num, double price);
	void sell(long num, double price);
	void update(double price);
	void show();
};
#endif // !STOCK00_H_

几个公有函数的实现

//stock00.cpp--implementing the stock class
//version 00
#include<iostream>
#include"stock00.h"

void Stock::acquire(const std::string& co, long n, double pr)
{
	company = co;
	if (n<0)
	{
		std::cout << "输入股票的数量不正确" << company << "被设置为0";
		shares = 0;
	}
	else
	{
		shares = n;
	}
	share_val = pr;
	set_tot();
}

void Stock::buy(long num, double price)
{
	if (num<0)
	{
		std::cout << "股票的数量不能是负数" << "请求终止";
	}
	else
	{
		shares += num;
		share_val = price;
		set_tot();
	}
}
void Stock::sell(long num, double price)
{
	using std::cout;
	if (num<0)
	{
		cout << "股票的数量不能是负数" << "请求终止";
	}
	else if (num>shares)
	{
		cout << "你输入的数量超过你持有的数量" << "请求终止"<<"\n";
	}
	else
	{
		shares -= num;
		share_val = price;
		set_tot();
	}
}

void Stock::update(double price)
{
	share_val = price;
	set_tot();
}

void Stock::show()
{
	using std::cout;
	using std::ios_base;

	//设置输入格式 #.###
	ios_base::fmtflags orig = cout.setf(ios_base::fixed, ios_base::floatfield);
	std::streamsize prec = cout.precision(3);

	cout << "公司 " << company
		<< "股票：" << shares << "\n"
		<< "股价：$" << share_val;

		//设置输出格式 #.##
		cout.precision(2);
		cout<< "总价值：$" << total_val << "\n";

		//回复原始格式
		cout.setf(orig, ios_base::floatfield);
		cout.precision(prec);
}

主函数的实现

#pragma region 练习1.10.3
//usestck0.cpp -- the client program
//compile with stock00.cpp
#if 1
#include <iostream>
#include"stock00.h"
int main()
{
	Stock fluffyTheCat;
	fluffyTheCat.acquire("NamoSmart", 20, 12.50);
	fluffyTheCat.show();
	fluffyTheCat.buy(15, 18.125);
	fluffyTheCat.show();
	fluffyTheCat.sell(400, 20.00);
	fluffyTheCat.show();
	fluffyTheCat.buy(300000, 40.125);
	fluffyTheCat.show();
	fluffyTheCat.sell(300000, 0.125);
	fluffyTheCat.show();
	return 0;
}
#endif 
#pragma endregion