我是堆栈溢出的新手，正在自学C++，但仍然是一个相当初学者。在完成了我正在使用的书的一大部分之后（这可能被认为是过时的和/或不是一本伟大的书）我决定通过自己尝试一些概念来重新实施它们，只有在需要的时候才参考这本书，但我似乎被卡住了。抽象数据类型（ADT），并将我的类的代码分成头文件（.h）和C++文件（.cpp）。提前为文字墙道歉，我只是想清楚和具体地说明我需要在哪里。
因此，我的目标是创建简单的形状类，这些形状类在适用的情况下相互继承。myPoly、myRectangle、myTriangle和mySquare。myPoly，如果我理解正确的话，应该是ADT，因为其中一个方法是纯虚函数（面积法），因为创建一个myPoly对象并不是我希望类的用户去做的事情。myRectangle和myTriangle都是从myPoly派生的，而mySquare又是从myRectangle派生的。我还包含了我的测试程序，我计划在那里测试我的类。我使用的是Code：：Blocks 10.05，当我构建test.cpp程序时，一直得到下面的错误：

undefined reference to 'myPoly::myPoly()'

我得到了42个类似的错误，都是关于myPoly类的方法。当我试图为myRectangle和myTriangle构建.cpp文件时，也会发生这种情况。通过对我在这个小项目中遇到的问题进行研究，我觉得我的包含保护或#include语句出了问题。有些东西没有被正确地包含或者被包含太多次了。一开始我把myPoly的.cpp文件提供给myRectangle和myTriangle，但在一些地方读到，包括myPoly的.h文件更有效，以及一些如何自动包括其. cpp。如果有人能提供一些见解，非常感谢。2我还记得在包含语句中使用引号和使用尖括号有什么不同。3下面是我为我的小项目制作的九个文件。大多数评论对我来说都是小纸条或提醒。

我的聚合物. h

//Practice with inheritance, polymorphism, and Abstract Data Types
//header file for Polygon class

#ifndef MYPOLY_H
#define MYPOLY_H

class myPoly
{
    public:
        //constructor
        //const reference pass because the values w and h don't change and reference avoid the time it takes to copy large
        //  objects by value (if there were any)
        myPoly();
        myPoly(const float & w, const float & h);

        //destructor
        virtual ~myPoly();

        //accessors
        float getWidth();
        float getHeight();
        void setWidth(const float & w);
        void setHeight(const float & h);

        virtual float area() = 0;

    private:
        float width, height;
};

#endif

我的聚合物. cpp

//Practice with inheritance, polymorphism, and Abstract Data Types
//implementation file for myPoly class

#include "myPoly.h"

//constructor
myPoly::myPoly()
{
    setWidth(10);
    setHeight(10);
}

myPoly::myPoly(const float & w, const float & h)
{
    setWidth(w);
    setHeight(h);
}

//destructor
myPoly::~myPoly() {}

//accessors
float myPoly::getWidth() {return width;}
float myPoly::getHeight() {return height;}

void myPoly::setHeight(const float & w) {width = w;}
void myPoly::setWidth(const float & h) {height = h;}

//pure virtual functions have no implementation
//area() is handled in the header file

我的矩形. h

//Practice with inheritance, polymorphism, and Abstract Data Types
//declaration file for myRectangle class

#ifndef MYRECTANGLE_H
#define MYRECTANGLE_H

#include "myPoly.h"

class myRectangle : public myPoly
{
    public:
        //constructor
        myRectangle();
        myRectangle(const float & w, const float & h);

        //destructor
        ~myRectangle();

        //this doesn't need to be virtual since the derived class doesn't override this method
        float area();
};

#endif

我的矩形. cpp

//Practice with inheritance, polymorphism, and Abstract Data Types
//implementaion file for the myRectangle class

//get a vauge compiler/linker error if you have virtual methods that aren't implemented (even if it ends up being just
//  a 'stub' method, aka empty, like the destructor)

#include "myRectangle.h"

myRectangle::myRectangle()
{
    setWidth(10);
    setHeight(10);
}

myRectangle::myRectangle(const float & w, const float & h)
{
    setWidth(w);
    setHeight(h);
}

myRectangle::~myRectangle()
{
}

float myRectangle::area()
{
    return getWidth() * getHeight();
}

我的三角形. h

//Practice with inheritance, polymorphism, and Abstract Data Types
//declaration file for myTriangle class

#ifndef MYTRIANGLE_H
#define MYTRIANGLE_H

#include "myPoly.h"

//imagine the triangle is a right triangle with a width and a height
//  |\
//  | \
//  |  \
//  |___\

class myTriangle : public myPoly
{
    public:
        //constructors
        myTriangle();
        myTriangle(const float & w, const float & h);

        //destructor
        ~myTriangle();

        //since nothing derives from this class it doesn't need to be virtual and in turn neither does the destructor
        float area();
};

#endif

我的三角形. cpp

//Practice with inheritance, polymorphism, and Abstract Data Types
//implementation file for myTriangle class

#include "myTriangle.h"

myTriangle::myTriangle()
{
    setWidth(10);
    setHeight(10);
}

myTriangle::myTriangle(const float & w, const float & h)
{
    setWidth(w);
    setHeight(h);
}

myTriangle::~myTriangle()
{
}

float myTriangle::area()
{
    return getWidth() * getHeight() / 2;
}

我的广场. h

//Practice with inheritance, polymorphism, and Abstract Data Types
//declaration file for mySquare class

#ifndef MYSQUARE_H
#define MYSQUARE_H

#include "myRectangle.cpp"

class mySquare : public myRectangle
{
    public:
        //constructors
        mySquare();
        //explicity call the myRectangle constructor within this implementation to pass w as width and height
        mySquare(const float w);

        //destructor
        ~mySquare();
};

#endif

我的广场. cpp

//Practice with inheritance, polymorphism, and Abstract Data Types
//implementation file for mySquare class

#include "mySquare.h"

mySquare::mySquare()
{
    setWidth(10);
    setHeight(10);
}

mySquare::mySquare(const float w)
{
    myRectangle::myRectangle(w, w);
}

mySquare::~mySquare()
{
}

测试. cpp

//Practice with inheritance, polymorphism, and Abstract Data Types
//main class that uses my shape classes and experiments with inheritance, polymorphism, and ADTs

#include "myRectangle.cpp"
//#include "mySquare.cpp"
#include "myTriangle.cpp"

#include <iostream>

int main()
{
    myPoly * shape = new myRectangle(20,20);

    return 0;
}

我非常好奇为什么我会得到这些错误，或者为什么我所做的事情可能不被认为是好的/最佳实践，而不是仅仅接收一行代码来使我的错误消失。