軟件的設計模式中,有個依賴倒轉原則(Dependence Inversion Principle,DIP),比較實用,下面介紹它。
一、依賴倒轉原則的定義
依賴抽象(接口),不要依賴具體的實現(類),也就是針對接口編程。
二、案例
1.1 原設計 ver1.1
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;
class Benz
{
public:
void run(){
cout << "奔馳開起來了";
}
};
class BMW
{
public:
void run(){
cout << "BMW開起來了";
}
};
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 加入了依賴倒轉原則的設計 ver1.2
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;
//---------------- 抽象層 --------------------
class Car
{
public:
virtual void run() = 0;
};
class Driver
{
public:
virtual void drive() = 0;
};
//---------------- 實現層 --------------------
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開車了" << endl;
car->run();
}
Car *car;
};
class Li4 :public Driver
{
public:
Li4(Car *car){
this->car = car;
}
virtual void drive(){
cout << "Li4開車了" << endl;
car->run();
}
Car *car;
};
//---------------- 業務邏輯層 --------------------
int main(void)
{
//讓Zhang3開奔馳
Car *benz = new Benz;
Driver *zhang3 = new Zhang3(benz);
zhang3->drive();
//讓李4開寶馬
Car *bmw = new BMW;
Driver *li4 = new Li4(bmw);
li4->drive();
return 0;
}
版本ver1.2 比ver1.1代碼的可維護性、可擴展性要好。