装饰模式

23 Aug 2017

在不改变原有实现的基础上，实现功能的扩展。并且可以多次叠加扩展。 被装饰者始终不变。装饰者在设定了要装饰对象以后也变成了一个被装饰者。

实例：咖啡店咖啡店有多种咖啡，每种有对应的价格。咖啡可以任意添加调味，比如，牛奶，糖，豆浆… 要计算加一份牛奶，两份糖的拿铁咖啡的价格。类图：

baseobject.h

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

class BaseObject{
public:
    BaseObject();
    virtual BaseObject();
    virtual float cost();
    void display();

protected:
    float value;
    string name;
};

baseobject.cc

#include "baseobject.h"

BaseObject::BaseObject(){
    this->value = 0;
}

BaseObject::BaseObject(){

}

float BaseObject::cost(){
    return value;
}

void BaseObject::display(){
    cout << this->name << " : " << this->value << endl;
}

americano.h

#include <iostream>
#include "baseobject.h"
using namespace std;

class Americano : public BaseObject{
public:
    Americano();
    Americano();
};

americano.cc

#include "americano.h"
Americano::Americano(){
    value = 12.5;
    name = "Americano";
    display();
}
Americano::Americano(){
    cout << "delete Americano" <<endl;
}

flavourobject.h

#include <iostream>
#include "../coffee/baseobject.h"
using namespace std;

class Flavourobject : public BaseObject{
public:
    Flavourobject();
    Flavourobject();
    
    virtual void setComponent(BaseObject * obj);
    virtual float cost();

protected:
    BaseObject * obj;
};

flavourobject.cc

#include "flavourobject.h"

Flavourobject::Flavourobject(){
    value = 3;
}

Flavourobject::Flavourobject(){

}

float Flavourobject::cost(){
    return this->value + this->obj->cost();
}

void Flavourobject::setComponent(BaseObject * obj){
    this->obj = obj;
}

milk.h

#include <iostream>
#include "../coffee/baseobject.h"
#include "../flavour/flavourobject.h"
using namespace std;

class Milk : public Flavourobject{
public:
    Milk();
    Milk();
};

milk.cc

#include "milk.h"

Milk::Milk(){
    value = 3;
    name = "Milk";
    display();
}

Milk::Milk(){

}

suger.h

#include <iostream>
#include "../coffee/baseobject.h"
#include "../flavour/flavourobject.h"
using namespace std;

class Suger : public Flavourobject{
public:
    Suger();
    Suger();
};

main.cc

#include <iostream>
#include "coffee/baseobject.h"
#include "coffee/americano.h"
#include "flavour/milk.h"
#include "flavour/suger.h"

using namespace std;

int main() {
    BaseObject * obj = new Americano();
    Flavourobject * flavour = new Milk();
    flavour->setComponent(obj);
    cout << "total:" << flavour->cost() << endl;
    Flavourobject * flavour1 = new Suger();
    flavour1->setComponent(dynamic_cast<BaseObject*>(flavour));
    cout << "total1:" << flavour1->cost() << endl;
    std::cout << "Hello, World!" << std::endl;
    return 0;
}

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装饰模式