设计模式之Bridge模式的C++实现

1、Bridge模式的提出

2、Bridge模式的定义

3、Bridge模式总结

4、需求描述

5、多继承方式实现

6、使用Bridge设计模式实现

1、Bridge模式的提出

在软件功能模块设计中，如果类的实现功能划分不清晰，使得继承得到的子类往往是随着需求的变化，子类急剧膨胀，充斥重复代码。将类要实现功能划分清楚是设计较好软件框架的关键。

2、Bridge模式的定义

对于类的实现功能具有两个变化的维度，甚至由多个维度的变化，使用类的多继承实现方式，会使子类数目急剧膨胀。Bridge模式使用“对象间的组合关系”解耦抽象和实现之间固有的绑定关系，使得抽象和实现可以沿着各自的维度变化，即将不同的维度分别进行抽象，然后各自根据变化维度进行继承。

3、Bridge模式总结

Bridge模式的应用一般在“两个非常强的变化维度”，有时一个类甚至有多个变化的维度，这时使用Bridge模式的扩展模式来设计代码。

4、需求描述

手机有固有属性（材料、颜色、摄像头个数）和软件属性（开机动画、网络打印、支持app数目）。有2款A、B类型手机，A、B分别继承手机的固有属性功能。在A款基础上又有2款Higher、Pro类型，Higher、Pro分别继承手机的软件功能；在B款的基础上也有2种Higher、Pro，这2种也分别继承手机的软件功能。

5、多继承方式实现

#include <iostream>class MobilePhone
{
public://手机材质virtual void PhoneMaterial()=0;//手机颜色virtual void PhoneColor()=0;//手机大小virtual void PhoneCameNum()=0;//开机动画virtual void BootAnimation()=0;//网络打印类型virtual void NetPrintType()=0;//软件支持数目virtual void SoftSuppotNum()=0;virtual ~MobilePhone(){};};//下面的类继承关系中，不同层级的类继承不同抽象函数，可以分函数抽象一个类，见Bridge模式。class APhoneNoraml:public MobilePhone
{
public:virtual ~APhoneNoraml(){};virtual void PhoneMaterial()override{std::cout << "Glass material" << std::endl;};virtual void PhoneColor()override{std::cout << "2 Colors" << std::endl;};virtual void PhoneCameNum()override{std::cout << "2 CamNum" << std::endl;};
};class BPhoneNoraml:public MobilePhone
{
public:virtual ~BPhoneNoraml(){};virtual void PhoneMaterial()override{std::cout << "Glass material" << std::endl;};virtual void PhoneColor()override{std::cout << "3 Colors" << std::endl;};virtual void PhoneCameNum()override{std::cout << "3 CamNum" << std::endl;};
};class APhoneHiger:public APhoneNoraml
{
public:virtual ~APhoneHiger(){};virtual void BootAnimation()override{APhoneNoraml::PhoneMaterial();APhoneNoraml::PhoneColor();APhoneNoraml::PhoneCameNum();std::cout << "good luck" << std::endl;};virtual void NetPrintType()override{std::cout << "Support base txt type" << std::endl;};virtual void SoftSuppotNum()override{std::cout << "Support 20 app" << std::endl;};
};class BPhoneHiger:public BPhoneNoraml
{
public:virtual ~BPhoneHiger(){};virtual void BootAnimation()override{BPhoneNoraml::PhoneMaterial();BPhoneNoraml::PhoneColor();BPhoneNoraml::PhoneCameNum();std::cout << "gook lunck" << std::endl;};virtual void NetPrintType()override{std::cout << "Support base txt type" << std::endl;};virtual void SoftSuppotNum()override{std::cout << "Support 20 app" << std::endl;};};class APhonePro:public APhoneNoraml
{
public:virtual ~APhonePro(){};virtual void BootAnimation()override{APhoneNoraml::PhoneMaterial();APhoneNoraml::PhoneColor();APhoneNoraml::PhoneCameNum();std::cout << "best wishes" << std::endl;};virtual void NetPrintType()override{std::cout << "Support base 3 type" << std::endl;};virtual void SoftSuppotNum()override{std::cout << "Support 30 app" << std::endl;};
};class BPhonePro:public BPhoneNoraml
{
public:virtual ~BPhonePro(){};virtual void BootAnimation()override{BPhoneNoraml::PhoneMaterial();BPhoneNoraml::PhoneColor();BPhoneNoraml::PhoneCameNum();std::cout << "best wishes" << std::endl;};virtual void NetPrintType()override{std::cout << "Support base 3 type" << std::endl;};virtual void SoftSuppotNum()override{std::cout << "Support 30 app" << std::endl;};};int main()
{MobilePhone* higherA = new APhoneHiger();higherA->BootAnimation();higherA->NetPrintType();higherA->SoftSuppotNum();delete higherA;higherA = nullptr;MobilePhone* proA = new APhonePro();proA->BootAnimation();proA->NetPrintType();proA->SoftSuppotNum();delete proA;proA = nullptr;return 0;
}

运行结果如下：

6、使用Bridge设计模式实现

#include <iostream>//将第一个变化维度的三个函数抽象成一个类，供第二层继承使用
class MobilePhone
{
public://手机材质virtual void PhoneMaterial()=0;//手机颜色virtual void PhoneColor()=0;//手机大小virtual void PhoneCameNum()=0;virtual ~MobilePhone(){}
};//将第二个变化维度的三个函数抽象出一个类，供第三层继承使用
class MobileSoft
{
public:MobileSoft(MobilePhone* p):Imp(p){};MobilePhone *Imp;//开机动画virtual void BootAnimation()=0;//网络打印类型virtual void NetPrintType()=0;//软件支持数目virtual void SoftSuppotNum()=0;
};class APhoneNoraml:public MobilePhone
{
public:virtual ~APhoneNoraml(){};virtual void PhoneMaterial()override{std::cout << "Glass material" << std::endl;};virtual void PhoneColor()override{std::cout << "2 Colors" << std::endl;};virtual void PhoneCameNum()override{std::cout << "2 CamNum" << std::endl;};
};class BPhoneNoraml:public MobilePhone
{
public:virtual ~BPhoneNoraml(){};virtual void PhoneMaterial()override{std::cout << "Glass material" << std::endl;};virtual void PhoneColor()override{std::cout << "3 Colors" << std::endl;};virtual void PhoneCameNum()override{std::cout << "3 CamNum" << std::endl;};
};//在第三层继承关系处使用对象组合。
class PhoneHiger:public MobileSoft
{
public:PhoneHiger(MobilePhone *p):MobileSoft(p){};virtual ~PhoneHiger(){};virtual void BootAnimation()override{Imp->PhoneMaterial();Imp->PhoneColor();Imp->PhoneCameNum();std::cout << "good luck" << std::endl;};virtual void NetPrintType()override{std::cout << "Support base txt type" << std::endl;};virtual void SoftSuppotNum()override{std::cout << "Support 20 app" << std::endl;};
};class PhonePro:public MobileSoft
{
public:PhonePro(MobilePhone *p):MobileSoft(p){};virtual ~PhonePro(){};virtual void BootAnimation()override{Imp->PhoneMaterial();Imp->PhoneColor();Imp->PhoneCameNum();std::cout << "best wishes" << std::endl;};virtual void NetPrintType()override{std::cout << "Support base 3 type" << std::endl;};virtual void SoftSuppotNum()override{std::cout << "Support 30 app" << std::endl;};
};int main()
{std::cout << " ************** PhoneHiger ************** " << std::endl;MobilePhone *normalA = new APhoneNoraml();MobileSoft *higherA = new PhoneHiger(normalA);higherA->BootAnimation();higherA->NetPrintType();higherA->SoftSuppotNum();std::cout << "\n ************** PhonePro ************** " << std::endl;MobilePhone *normalPro = new APhoneNoraml();MobileSoft *proA = new PhonePro(normalPro);proA->BootAnimation();proA->NetPrintType();proA->SoftSuppotNum();return 0;
}

运行结果如下：