建造者模式
前序
小菜和大鳥兩人出去吃夜宵，大鳥要了份炒飯，小菜要了份炒面。炒完后大鳥看到炒面感覺不錯，于是也叫了一份。大鳥嘗后感覺淡而無味，于是便問小菜：“為什么你的炒面好吃，而我再要的炒面卻沒有放鹽？這好吃不好吃是由誰決定的？”小菜答道：“當然是燒菜的人，他感覺好，就是一盤好面，要是心情不好，或者粗心大意，就是一盤垃圾。”“：）好，那再想想，老麥老肯他們的產品，味道是由什么決定的？”“我知道，那是由他們的工作流程決定的，由于他們制定了非常規范的工作流程，原料放多少，加熱幾分鐘，都有嚴格規定，估計放多少鹽都是用克來計量的。而這個工作流程是在所有的門店都必須要遵照執行的，所以我們吃到的東西不管在哪在什么時候味道都一樣。這里我們要吃的食物都依賴工作流程。”
于是大鳥出題讓小菜實現一個畫小人的程序。
建造小人第一版
#include <stdio.h>
class Graphics
{
public:
void DrawEllipse(int x1,int y1,int x2,int y2)
{
printf("DrawEllipse %d,%d,%d,%d\n",x1,y1,x2,y2);
}
void DrawRectangle(int x1,int y1,int x2,int y2)
{
printf("DrawRectangle %d,%d,%d,%d\n",x1,y1,x2,y2);
}
void DrawLine(int x1,int y1,int x2,int y2)
{
printf("DrawLine %d,%d,%d,%d\n",x1,y1,x2,y2);
}
};
class PersonThinBuilder
{
public:
PersonThinBuilder(Graphics _g) : g(_g){}
void Build()
{
g.DrawEllipse(50,20,30,30);
g.DrawRectangle(60,50,10,50);
g.DrawLine(60,50,40,100);
g.DrawLine(70,50,90,100);
g.DrawLine(60,100,45,150);
g.DrawLine(70,100,85,150);
}
protected:
Graphics g;
};
class PersonFatBuilder
{
public:
PersonFatBuilder(Graphics _g) : g(_g){}
void Build()
{
g.DrawEllipse(50,20,30,30);
g.DrawEllipse(60,50,10,50);
g.DrawLine(60,50,40,100);
g.DrawLine(70,50,90,100);
g.DrawLine(60,100,45,150);
g.DrawLine(70,100,85,150);
}
protected:
Graphics g;
};
int main()
{
Graphics gThin,gFat;
PersonThinBuilder* ptb = new PersonThinBuilder(gThin);
ptb->Build();
PersonFatBuilder* pfb = new PersonFatBuilder(gFat);
pfb->Build();
delete ptb;
delete pfb;
return 0;
}
“炒面忘記放鹽的問題依然沒有解決。比如我們現在需要你加一個高個的小人，你會不會因為編程不注意，又讓他缺胳膊少腿呢？”
“是呀，最好的辦法是規定，凡是建造小人，都必須要有頭和身體，以及兩收兩腳。”
建造者模式
將產品的內部表象和產品的生成過程分割開來，從而使一個建造過程生成具有不同的內部表象的產品對象。建造模式使得產品內部表象可以獨立的變化，客戶不必知道產品內部組成的細節。建造模式可以強制實行一種分步驟進行的建造過程。
實現方式(UML類圖)
實現代碼
#include <stdio.h>
class Graphics
{
public:
void DrawEllipse(int x1,int y1,int x2,int y2)
{
printf("DrawEllipse %d,%d,%d,%d\n",x1,y1,x2,y2);
}
void DrawRectangle(int x1,int y1,int x2,int y2)
{
printf("DrawRectangle %d,%d,%d,%d\n",x1,y1,x2,y2);
}
void DrawLine(int x1,int y1,int x2,int y2)
{
printf("DrawLine %d,%d,%d,%d\n",x1,y1,x2,y2);
}
};
class PersonBuilder
{
public:
PersonBuilder(Graphics _g) : g(_g){}
virtual void BuildHead()=0;
virtual void BuildBody()=0;
virtual void BuildArmLeft()=0;
virtual void BuildArmRight()=0;
virtual void BuildLegLeft()=0;
virtual void BuildLegRight()=0;
protected:
Graphics g;
};
class PersonThinBuilder : public PersonBuilder
{
public:
PersonThinBuilder(Graphics g) : PersonBuilder(g){}
virtual void BuildHead()
{
g.DrawEllipse(50,20,30,30);
}
virtual void BuildBody()
{
g.DrawRectangle(60,50,10,50);
}
virtual void BuildArmLeft()
{
g.DrawLine(60,50,40,100);
}
virtual void BuildArmRight()
{
g.DrawLine(70,50,90,100);
}
virtual void BuildLegLeft()
{
g.DrawLine(60,100,45,150);
}
virtual void BuildLegRight()
{
g.DrawLine(70,100,85,150);
}
};
class PersonFatBuilder : public PersonBuilder
{
public:
PersonFatBuilder(Graphics g) : PersonBuilder(g){}
virtual void BuildHead()
{
g.DrawEllipse(50,20,30,30);
}
virtual void BuildBody()
{
g.DrawEllipse(60,50,10,50);
}
virtual void BuildArmLeft()
{
g.DrawLine(60,50,40,100);
}
virtual void BuildArmRight()
{
g.DrawLine(70,50,90,100);
}
virtual void BuildLegLeft()
{
g.DrawLine(60,100,45,150);
}
virtual void BuildLegRight()
{
g.DrawLine(70,100,85,150);
}
};
class PersonDirector
{
public:
PersonDirector(PersonBuilder* _pb) : pb(_pb){}
void CreatePerson()
{
pb->BuildHead();
pb->BuildBody();
pb->BuildArmLeft();
pb->BuildArmRight();
pb->BuildLegLeft();
pb->BuildLegRight();
}
protected:
PersonBuilder* pb;
};
int main()
{
Graphics gThin,gFat;
PersonThinBuilder* ptb = new PersonThinBuilder(gThin);
PersonDirector* pdThin = new PersonDirector(ptb);
pdThin->CreatePerson();
PersonFatBuilder* pfb = new PersonFatBuilder(gFat);
PersonDirector* pdFat = new PersonDirector(pfb);
pdFat->CreatePerson();
delete ptb;
delete pdThin;
delete pfb;
delete pdFat;
return 0;
}
運行結果
所有文件打包下載
posted on 2011-06-02 17:34
lwch 閱讀(1871)
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設計模式