软件里的依赖倒转原则

        软件的设计模式中，有个依赖倒转原则(Dependence Inversion Principle,DIP)，比较实用，下面介绍它。
        一、依赖倒转原则的定义
        依赖抽象(接口)，不要依赖具体的实现(类)，也就是针对接口编程。
        二、案例
        1.1 原设计 ver1.1

#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
using namespace std;

class Benz
{
    
    
public:
	void run(){
    
    
		cout << "奔驰开起来了";
	}
};

class BMW
{
    
    
public:
	void run(){
    
    
		cout << "BMW开起来了";
	}
};

class Zhang3
{
    
    
public:
	Zhang3(Benz *benz) {
    
    
		this->benz = benz;
	}

	void driveBenz() {
    
    
		benz->run();
	}

	void driveBMW() {
    
    
		bmw->run();
	}

private:
	Benz *benz;
	BMW  *bmw;
};



int main(void)
{
    
    
	Benz benz;
	Zhang3 zhang3(&benz);
	zhang3.driveBenz();

	return 0;
}

        1.2 加入了依赖倒转原则的设计 ver1.2

#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
using namespace std;

//---------------- 抽象层 --------------------
class Car
{
    
    
public:
	virtual void run() = 0;
};

class Driver
{
    
    
public:
	virtual void drive() = 0;
};

//---------------- 实现层 --------------------
class Benz :public Car
{
    
    
public:
	virtual void run(){
    
    
		cout << "benz run..." << endl;
	}
};

class BMW :public Car
{
    
    
public:
	virtual void run(){
    
    
		cout << "BMW run..." << endl;
	}
};

class Zhang3 :public Driver
{
    
    
public:
	Zhang3(Car *car){
    
    
		this->car = car;
	}

	virtual void drive(){
    
    
		cout << "Zhang3开车了" << endl;
		car->run();
	}

	Car *car;
};

class Li4 :public Driver
{
    
    
public:
	Li4(Car *car){
    
    
		this->car = car;
	}

	virtual void drive(){
    
    
		cout << "Li4开车了" << endl;
		car->run();
	}

	Car *car;
};

//---------------- 业务逻辑层 --------------------
int main(void)
{
    
    

	//让Zhang3开奔驰
	Car *benz = new Benz;
	Driver *zhang3 = new Zhang3(benz);

	zhang3->drive();

	//让李4开宝马
	Car *bmw = new BMW;
	Driver *li4 = new Li4(bmw);
	li4->drive();

	return 0;
}

        版本ver1.2 比ver1.1代码的可维护性、可扩展性要好。