概念
装饰模式又叫包装模式。通过一种对客户端透明的方式来扩展对象功能,是继承关系的一个替换方案。
装饰模式就是把要添加的附加功能分别放在单独的类中,并让这个类包含它要装饰的对象,当需要执行时,客户端就可以有选择地、按顺序地使用装饰功能包装对象。
类图角色和职责
![](https://img.laitimes.com/img/__Qf2AjLwojIjJCLyojI0JCLiQ3chVEa0V3bT9CX5RXa2Fmcn9CXwczLcVmds92czlGZvwVP9EUTDZ0aRJkSwk0LcxGbpZ2LcBDM08CXlpXazRnbvZ2LcRlMMVDT2EWNvwFdu9mZvwVPFdFZvlzVZ9mTYR2bwNjW1x2RkZXUYpVd1kmYr50MZV3YyI2cKJDT29GRjBjUIF2LcRHelR3LcJzLctmch1mclRXY39DM3cjMxkjMxITOwYDM3EDMy8CX0Vmbu4GZzNmLn9Gbi1yZtl2Lc9CX6MHc0RHaiojIsJye.jpg)
适用于:装饰着模式(Decorator Pattern)动态的给一个对象添加一些额外的职责。就增加功能来说,此模式比生成子类更为灵活。
案例
#include <iostream>
using namespace std;
class Car
{
public:
virtual void show() = 0;
};
class RunCar:public Car
{
public:
void run()
{
cout << "可以跑" << endl;
}
virtual void show()
{
run();
}
};
class SwimCarDirector:public Car
{
public:
SwimCarDirector(Car *p)
{
m_p = p;
}
void swim()
{
cout << "可以游泳" << endl;
}
virtual void show()
{
m_p->show();
swim();
}
private:
Car *m_p;
};
class FlyCarDirector:public Car
{
public:
FlyCarDirector(Car *p)
{
m_p = p;
}
void fly()
{
cout << "可以飞" << endl;
}
virtual void show()
{
m_p->show();
fly();
}
private:
Car *m_p;
}
int main(void)
{
Car *runcar = NULL;
runcar = new RunCar();
runcar->show();
cout << "车开始装饰swim" << endl;
SwimCarDirector *swimCar = new SwimCarDirector(runcar);
swimCar->show();
cout << "车开始装饰fly" << endl;
FlyCarDirector *flyCar= new FlyCarDirector(runcar);
flyCar->show();
delete flyCar;
delete swimCar;
delete runCar;
return 0;
}