函数中未解决的外部符号错误不知道如何解决

问题描述

我的代码中出现错误“未解析的外部符号”。这特别发生在我的 .cpp 文件中的 setCoefficient() 函数中。

我正在尝试使用动态数组创建多项式的表示。我设置事物的方式是数组的索引对应于项的幂，并且存储在该特定索引处的值是该项的系数。

在我的 setCoefficient() 函数中，我试图根据用户是否尝试添加大于我的数组当前可以容纳的系数/幂来确定我是否需要调整数组的大小。如果我确定需要重新调整数组大小，我会创建一个新数组并将旧数组的内容复制到新的更大的数组中。但是，当我尝试编译我的函数时遇到了以下错误：

"Error LNK2019 unresolved external symbol "public: __thiscall Poly::Poly(class Poly const &)" (??0Poly@@QAE@ABV0@@Z) re"

并且不确定如何解决它。如果我注释掉我的 setCoefficient() 函数，错误就会消失，所以我确定错误源于该函数。有人可以帮助我确定我的函数中导致该错误的原因吗？

这是我的 .cpp 实现文件：

#include "poly.h"

//Default constructor. Initializes a Poly to: 0x^0
Poly::Poly()
{
    cout << "No parameter constructor called" << endl;
    polyArray = new int[1];
    //polyArray[1] = 0;
    polyArray[0] = 0;
    length = 0;
}

//Constructor with one argument. Initialized to: coefficientx^0
Poly::Poly(int coefficient)
{
    cout << "One parameter constructor called" << endl;
    cout << "coefficient: " << coefficient << endl;
    polyArray = new int[1];
    //polyArray[1] = 0;
    polyArray[0] = coefficient;
    length = 0;
}

//Constructor with two arguments. Initialized to: coefficientx^power
Poly::Poly(int coefficient,int power)
{
    cout << "Two parameter constructor called" << endl;
    cout << "power: " << power << endl;
    cout << "coeff: " << coefficient << endl;
    polyArray = new int[power]; //I think I need to add 1 here to account for that fact that arrays start at index 0.
    
    for (int i = 0; i < power; i++) { //I want to initialize the dynamic array to all 0's
        polyArray[i] = 0;
    }

    polyArray[power] = coefficient;
    length = power;
}

//Destructor
Poly::~Poly()
{
    cout << "I am the destructor" << endl;
    polyArray = NULL;
    delete [] polyArray;
}

ostream& operator<<(ostream& out,const Poly& p)
{
    for (int i=p.length; i>=0; i--) {
        if (p.polyArray[i] == 0 && i == 0 && p.length == 0) {
            cout << "0";
        }
        else if (p.polyArray[i] == 0) {
            cout << "";
        }
        else if(i==0 && p.polyArray!=0){
            cout << p.polyArray[i];
        }
        else {
            cout << p.polyArray[i] << "^" << i;
        }
    }
    return out;
}

Poly Poly::setCoefficient(const int coefficient,const int power) {
    if (power > this->length){
        Poly largerPolyArray(0,power * 2);
        largerPolyArray.length = power * 2;
        //Here I am creating a dynamic array that is twice as large as the power.
        //This is wasteful,but it works
        for (int i = 0; i < this->length; i++) {
            largerPolyArray.polyArray[i] = this->polyArray[i];
        }
        largerPolyArray.polyArray[power] = coefficient;
        return largerPolyArray;
    }
    else {
        this->polyArray[power] = coefficient;
        return *this;
    }
}

这是我的这个项目的 .h 文件：

//A Poly class
#ifndef Poly_H                                  
#define Poly_H
#include <iostream>
#include <string>

using namespace std;

class Poly {
    friend ostream& operator<<(ostream& out,const Poly& p);
    friend istream& operator>>(istream& in,Poly& p);

public:
    //Member functions
    Poly(); //Default constructor. Initializes a Poly to: 0x^0
    Poly(int coefficient); //Constructor with one argument. Initialized to: coefficientx^0
    Poly(int coefficient,int power); //Constructor with two arguments. Initialized to: coefficientx^power
    Poly(const Poly& p); //Copy constructor. Creates a deep copy of a Poly.
    ~Poly(); //Destructor


    int degree() const; //Returns the largest degree term in a Poly.
    double getCoefficient(const int power) const; //returns the coefficient of the x^power term.
    Poly setCoefficient(const int coefficient,const int power); //Sets the coefficient of the term indicated by the power.


    // Arithmetic operators
    Poly operator+(const Poly& p) const;
    Poly operator-(const Poly& p) const;

    // Boolean comparison operators
    bool operator==(const Poly& p) const;
    bool operator!=(const Poly& p) const;

    // Assignment operators
    Poly& operator=(const Poly& p);

    Poly& operator+=(const Poly& p);
    Poly& operator-=(const Poly& p);
    Poly& operator*=(const Poly& p);

    //Clean up/delete all Poly terms.
    void clear();
    //Checks if the Poly is empty or not.
    bool isEmpty() const;

private:
    int length; //# of terms in the Poly/size of the array
    int* polyArray;
};

#endif

解决方法

您已经在头文件中声明了 Poly::Poly(const Poly& p);（它应该创建一个 Poly 的深层副本），但是您还没有在 .cpp 文件中定义它。>