设计模式初探3——装饰者模式（Observer Pattern）

#include <iostream>
#include <string>
using namespace std;

class Toy {
public:
    virtual string getDescription() = 0;
};

class Duck : public Toy {
public:
    string getDescription(){ return "I'm a simple Toy-Duck. "; }
}; 

class Decorator : public Toy {
public:
    Decorator(Toy* t) : toy(t){}
protected:
    Toy* toy;
};

class ShapeDecorator : public Decorator {
public:
    ShapeDecorator(Toy* t) : Decorator(t){}
    string getDescription() {
        return toy->getDescription.append("Now I have new shape. ");
    }
};

class SoundDecorator : public Decorator {
public:
    SoundDecorator(Toy* t) : Decorator(t){}
    string getDescription() {
        return toy->getDescription.append("Now I can quack. ");
    }
};

int main()    
{    
    Toy *toy = new Duck();
    cout << toy->getDescription();

    toy = new ShapeDecorator(toy);
    cout << toy->getDescription();
    
    toy = new SoundDecorator(toy);
    cout << toy->getDescription();   
    return 0;    
}