關於建造者模式（C++實現）——怎麼做一個全家桶

關於建造者模式，專業的術語介紹可以直接戳到菜鳥教程去學習——菜鳥教程~建造者模式

談談個人體會

建造者模式簡直就是爲全家桶系列而生的，它使用一個個簡單的對象進而構成複雜的對象，就像肯德基使用簡單的薯條、雞腿、雞翅、可樂等單一的食物推出了全家桶套餐。後序又將各種單一的產品進行組合他，不斷推出全新的套餐，拉動消費。
屁話不多說了，下面介紹下我學習建造者模式後，用C++描述的一個簡單demo。

UML圖

強推一波staruml，這軟件確實有丶東西，除了根據代碼反向生成UML圖不夠精準（當然也可以說是我寫的狗屁東西不符合人家的標準，狗頭.jpg），但是它對於一個對象的各種描述真的是相當到位了，對於上手UML圖絕對是利器。
飲料和漢堡是抽象類，各自派生出自己的產品，而它們和建造者又是聚合關係。離開了建造者它們也可以生活得很好。

代碼

builder_mode.h

#pragma once

#include <string>
using namespace std;

class hamburger
{
protected:
	int m_price;
public:
	virtual int show_price() = 0;
};

class chicken_hamburger:public hamburger
{
public:
	//不能使用列表形式初始化從基類繼承的成員變量
	chicken_hamburger(int price = 10)
	{
		m_price = price;
	}
	int show_price()
	{
		return m_price;
	}
};

class beef_hamburger:public hamburger
{
public:
	beef_hamburger(int price = 12)
	{
		m_price = price;
	}
	int show_price()
	{
		return m_price;
	}
};

class drink
{
protected:
	int m_price;
public:
	virtual int show_price() = 0;
};

class cola:public drink
{
public:
	cola(int price = 5)
	{
		m_price = price;
	}
	int show_price()
	{
		return m_price;
	}
};

class juice:public drink
{
public:
	juice(int price = 8)
	{
		m_price = price;
	}
	int show_price()
	{
		return m_price;
	}
};

class builder
{
private:
	hamburger *m_hamburger;
	drink *m_drink;
	int m_price;
	string m_name;
public:
	builder()
	{
		m_hamburger = NULL;
		m_drink = NULL;
		m_price = 0;
	}
	~builder()
	{
		if (m_hamburger != NULL)
		{
			delete m_hamburger;
			m_hamburger = NULL;
		}
		if (m_drink != NULL)
		{
			delete m_drink;
			m_drink = NULL;
		}
	}
	void prepare_cola()
	{
		if (m_hamburger != NULL)
		{
			delete m_hamburger;
			m_hamburger = NULL;
		}
		if (m_drink != NULL)
		{
			delete m_drink;
			m_drink = NULL;
		}
		m_price = 0;
		m_drink = new cola;
		m_name = "cola";
	}
	void prepare_beef_hamburger()
	{
		if (m_hamburger != NULL)
		{
			delete m_hamburger;
			m_hamburger = NULL;
		}
		if (m_drink != NULL)
		{
			delete m_drink;
			m_drink = NULL;
		}
		m_price = 0;
		m_hamburger = new beef_hamburger;
		m_name = "beef_hamburger";
	}
	void prepare_beef_hamburger_with_cola()
	{
		if (m_hamburger != NULL)
		{
			delete m_hamburger;
			m_hamburger = NULL;
		}
		if (m_drink != NULL)
		{
			delete m_drink;
			m_drink = NULL;
		}
		m_price = 0;
		m_hamburger = new beef_hamburger(10);
		m_drink = new cola(3);
		m_name = "beef_hamburger_with_cola";
	}
	void prepare_chicken_hamburger_with_juice()
	{
		if (m_hamburger != NULL)
		{
			delete m_hamburger;
			m_hamburger = NULL;
		}
		if (m_drink != NULL)
		{
			delete m_drink;
			m_drink = NULL;
		}
		m_price = 0;
		m_hamburger = new chicken_hamburger(8);
		m_drink = new juice(6);
		m_name = "chicken_hamburger_with_juice";
	}
	int show_price()
	{
		if (m_drink != NULL)
			m_price += m_drink->show_price();
		if (m_hamburger != NULL)
			m_price += m_hamburger->show_price();
		return m_price;
	}
	string show_name()
	{
		return m_name;
	}
};

builder_mode.cpp

#include <iostream>
#include "builder_mode.h"
using namespace std;

int main(int argc, char const *argv[])
{
	builder buil;
	buil.prepare_chicken_hamburger_with_juice();
	cout << "name: " << buil.show_name() << endl;
	cout << "price: " << buil.show_price() << "RMB" <<endl;
	buil.prepare_cola();
	cout << "name: " << buil.show_name() << endl;
	cout << "price: " << buil.show_price() << "RMB" << endl;
	return 0;
}

恭喜自己，寫demo的時候又踩坑了，真的是一踩一個準，一踩一個爽鴨！
切記，派生類不能使用列表形式初始化從基類繼承過來的成員變量
這是爲什麼呢？

結果

什麼時候我也可以擁有一個全家桶，裏面啥都有…
醒醒，明天該上班寫bug了