C+；中工厂模式中的运行时错误+； 我最近从java切换到C++。 我正在尝试实现工厂设计模式

这是我的档案

Shape.h

    #pragma once

    class Ishape
    {
    public:
        virtual void draw()=0;
    };

    #pragma once
    #include"Shape.h"
    class Rectangle :public Ishape
    {
    public:
        void draw();
    };

    #pragma once
    #include"Shape.h"

    class Square :public Ishape
    {
    public:
        void draw();
    };

    #pragma once
    #include "Shape.h"
    #include<iostream>
    class ShapeFactory
    {
    public:
        static Ishape* getShape(std::string type);
    };

矩形.h

    #pragma once

    class Ishape
    {
    public:
        virtual void draw()=0;
    };

    #pragma once
    #include"Shape.h"
    class Rectangle :public Ishape
    {
    public:
        void draw();
    };

    #pragma once
    #include"Shape.h"

    class Square :public Ishape
    {
    public:
        void draw();
    };

    #pragma once
    #include "Shape.h"
    #include<iostream>
    class ShapeFactory
    {
    public:
        static Ishape* getShape(std::string type);
    };

---

矩形.cpp

    #include"Rectangle.h"
    #include<iostream>
    void draw()
    {
        std::cout << "Rectangle Draw" << std::endl;
    }

    #include"Square.h"
    #include<iostream>

    void draw()
    {
        std::cout << "Square Draw" << std::endl;
    }

    #include"ShapeFactory.h"
    #include"Rectangle.h"
    #include"Square.h"


    static Ishape* getShape(std::string type)
    {
        Ishape* s = nullptr;
        if (type == "Rectangle")
        {
            s= new Rectangle;
        }
        else if (type == "Square")
        {
            s= new Square;
        }
        return s;
    }

    #include<iostream>
    #include"ShapeFactory.h"
    int main()
    {
        using namespace std;
        Ishape* shape = ShapeFactory::getShape("Rectangle");
        shape->draw();
        return 0;
    }

#include"Rectangle.h"
#include<iostream>
void Rectangle::draw()
//   ^^^^^^^^^^^
{
    std::cout << "Rectangle Draw" << std::endl;
}

#include"Square.h"
#include<iostream>

void Square::draw()
//   ^^^^^^^^
{
    std::cout << "Square Draw" << std::endl;
}

#include"ShapeFactory.h"
#include"Rectangle.h"
#include"Square.h"


static Ishape* getShape(std::string type)
{
    Ishape* s = nullptr;
    if (type == "Rectangle")
    {
        s= new Rectangle;
    }
    else if (type == "Square")
    {
        s= new Square;
    }
    return s;
}

Square.cpp

    #include"Rectangle.h"
    #include<iostream>
    void draw()
    {
        std::cout << "Rectangle Draw" << std::endl;
    }

    #include"Square.h"
    #include<iostream>

    void draw()
    {
        std::cout << "Square Draw" << std::endl;
    }

    #include"ShapeFactory.h"
    #include"Rectangle.h"
    #include"Square.h"


    static Ishape* getShape(std::string type)
    {
        Ishape* s = nullptr;
        if (type == "Rectangle")
        {
            s= new Rectangle;
        }
        else if (type == "Square")
        {
            s= new Square;
        }
        return s;
    }

    #include<iostream>
    #include"ShapeFactory.h"
    int main()
    {
        using namespace std;
        Ishape* shape = ShapeFactory::getShape("Rectangle");
        shape->draw();
        return 0;
    }

#include"Rectangle.h"
#include<iostream>
void Rectangle::draw()
//   ^^^^^^^^^^^
{
    std::cout << "Rectangle Draw" << std::endl;
}

#include"Square.h"
#include<iostream>

void Square::draw()
//   ^^^^^^^^
{
    std::cout << "Square Draw" << std::endl;
}

#include"ShapeFactory.h"
#include"Rectangle.h"
#include"Square.h"


static Ishape* getShape(std::string type)
{
    Ishape* s = nullptr;
    if (type == "Rectangle")
    {
        s= new Rectangle;
    }
    else if (type == "Square")
    {
        s= new Square;
    }
    return s;
}

客户端代码：

Source.cpp

    #include"Rectangle.h"
    #include<iostream>
    void draw()
    {
        std::cout << "Rectangle Draw" << std::endl;
    }

    #include"Square.h"
    #include<iostream>

    void draw()
    {
        std::cout << "Square Draw" << std::endl;
    }

    #include"ShapeFactory.h"
    #include"Rectangle.h"
    #include"Square.h"


    static Ishape* getShape(std::string type)
    {
        Ishape* s = nullptr;
        if (type == "Rectangle")
        {
            s= new Rectangle;
        }
        else if (type == "Square")
        {
            s= new Square;
        }
        return s;
    }

    #include<iostream>
    #include"ShapeFactory.h"
    int main()
    {
        using namespace std;
        Ishape* shape = ShapeFactory::getShape("Rectangle");
        shape->draw();
        return 0;
    }

#include"Rectangle.h"
#include<iostream>
void Rectangle::draw()
//   ^^^^^^^^^^^
{
    std::cout << "Rectangle Draw" << std::endl;
}

#include"Square.h"
#include<iostream>

void Square::draw()
//   ^^^^^^^^
{
    std::cout << "Square Draw" << std::endl;
}

#include"ShapeFactory.h"
#include"Rectangle.h"
#include"Square.h"


static Ishape* getShape(std::string type)
{
    Ishape* s = nullptr;
    if (type == "Rectangle")
    {
        s= new Rectangle;
    }
    else if (type == "Square")
    {
        s= new Square;
    }
    return s;
}

#包括
#包括“ShapeFactory.h”
int main（）
{
使用名称空间std；
Ishape*shape=ShapeFactory:：getShape（“矩形”）；
形状->绘图（）；
返回0；
}

当我运行此操作时，出现以下运行时错误：

    Severity    Code    Description Project File    Line    Suppression State
    Error   LNK2005 "void __cdecl draw(void)" (?draw@@YAXXZ) already defined in Rectangle.obj       1   
    Error   LNK2019 unresolved external symbol "public: static class Ishape * __cdecl ShapeFactory::getShape(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (?getShape@ShapeFactory@@SAPAVIshape@@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) referenced in function _main Project1    C:\Users\nikhil\source\repos\Project1\Project1\Source.obj   1   
    Error   LNK1120 1 unresolved externals  Project1    C:\Users\nikhil\source\repos\Project1\Debug\Project1.exe    1   

严重性代码描述项目文件行抑制状态
错误LNK2005“void\uu cdecl draw（void）”（？draw@@YAXXZ）已在Rectangle.obj 1中定义
错误LNK2019未解析的外部符号“public:static类Ishape*uu cdecl ShapeFactory:：getShape（类std:：basic_字符串）”（？）？getShape@ShapeFactory@@SAPAVIshape@@V？$basic_string@DU？$char_traits@D@性病病毒$allocator@D@2@@std@@@Z）在函数\u main Project1 C:\Users\nikhil\source\repos\Project1\Project1\source.obj 1中引用
错误LNK1120 1未解析的外部项目1 C:\Users\nikhil\source\repos\Project1\Debug\Project1.exe 1

几点： 我读到将头文件和代码文件分开保存是一种很好的做法，这就是为什么我遵循这个原则

我遵循了这个工厂设计模式的例子

---

任何人都可以建议如何克服错误。C++中的其他技巧也会有帮助。

< P> <强>矩形。CPP

    #include"Rectangle.h"
    #include<iostream>
    void draw()
    {
        std::cout << "Rectangle Draw" << std::endl;
    }

    #include"Square.h"
    #include<iostream>

    void draw()
    {
        std::cout << "Square Draw" << std::endl;
    }

    #include"ShapeFactory.h"
    #include"Rectangle.h"
    #include"Square.h"


    static Ishape* getShape(std::string type)
    {
        Ishape* s = nullptr;
        if (type == "Rectangle")
        {
            s= new Rectangle;
        }
        else if (type == "Square")
        {
            s= new Square;
        }
        return s;
    }

    #include<iostream>
    #include"ShapeFactory.h"
    int main()
    {
        using namespace std;
        Ishape* shape = ShapeFactory::getShape("Rectangle");
        shape->draw();
        return 0;
    }

#include"Rectangle.h"
#include<iostream>
void Rectangle::draw()
//   ^^^^^^^^^^^
{
    std::cout << "Rectangle Draw" << std::endl;
}

#include"Square.h"
#include<iostream>

void Square::draw()
//   ^^^^^^^^
{
    std::cout << "Square Draw" << std::endl;
}

#include"ShapeFactory.h"
#include"Rectangle.h"
#include"Square.h"


static Ishape* getShape(std::string type)
{
    Ishape* s = nullptr;
    if (type == "Rectangle")
    {
        s= new Rectangle;
    }
    else if (type == "Square")
    {
        s= new Square;
    }
    return s;
}

---

你在面向对象方面做得很好。但显然你不理解C++的一般原理。当您在矩形中写入

void draw（）

时，cpp实际上是自由函数，但没有

Rectangle

的成员方法（在其他情况下类似）

这些是链接器错误而不是运行时错误。哦，我如何修复它们？您创建了两个名为

draw（）

的自由函数。它们与你的课程无关。链接器抱怨你违反了一个定义规则。你可能会感兴趣。“我最近从java切换到C++”——然后步骤一就是要忘记你所知道的关于java的一切，C++是一种全新的语言。语法上有相似之处，但就目前而言，看似相同的结构的语义通常是完全不同的。只是提示一下。矩形和正方形这两个类是从Ishape扩展而来的，它们定义了自己的绘图。我可以用它来应用polmorphism吗