建造者模式
前序
小菜和大鸟两人出去吃夜宵，大鸟要了份炒饭，小菜要了份炒面。炒完后大鸟看到炒面感觉不错，于是也叫了一份。大鸟尝后感觉淡而无味，于是便问小菜：“为什么你的炒面好吃，而我再要的炒面却没有放盐？这好吃不好吃是由谁决定的？”小菜答道：“当然是烧菜的人，他感觉好，就是一盘好面，要是心情不好，或者粗心大意，就是一盘垃圾。”“：）好，那再想想，老麦老肯他们的产品，味道是由什么决定的？”“我知道，那是由他们的工作流程决定的，由于他们制定了非常规范的工作流程，原料放多少，加热几分钟，都有严格规定，估计放多少盐都是用克来计量的。而这个工作流程是在所有的门店都必须要遵照执行的，所以我们吃到的东西不管在哪在什么时候味道都一样。这里我们要吃的食物都依赖工作流程。”
于是大鸟出题让小菜实现一个画小人的程序。
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;
}
“炒面忘记放盐的问题依然没有解决。比如我们现在需要你加一个高个的小人，你会不会因为编程不注意，又让他缺胳膊少腿呢？”
“是呀，最好的办法是规定，凡是建造小人，都必须要有头和身体，以及两收两脚。”
建造者模式
将产品的内部表象和产品的生成过程分割开来，从而使一个建造过程生成具有不同的内部表象的产品对象。建造模式使得产品内部表象可以独立的变化，客户不必知道产品内部组成的细节。建造模式可以强制实行一种分步骤进行的建造过程。
实现方式(UML类图)
实现代码
#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;
}
运行结果
所有文件打包下载
posted on 2011-06-02 17:34
lwch 阅读(1840)
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设计模式