C++ Linker 错误 function 已定义

Question

Have been stuck with multiple functions defined and linker errors while trying to compile the program, not too sure how I even defined everything properly in the header.

The purpose of the program is to check the validity of two entries from the main.cpp/test file. I made a program which checks the entries from the test file.

CarInventory.cpp

       #include <iostream>
       #include <string>
       #include <iomanip>
       #include <string.h>
       #include "CarInventory.h"
       using namespace std;
       using namespace sdds;
       void CarInventory::resetInfo()

      {

         m_type = nullptr;

         m_brand = nullptr;

         m_model = nullptr;

         m_year = 0;

         m_code = 0;

    m_price = 0;

}

CarInventory::CarInventory()

{

    resetInfo();

}

CarInventory::CarInventory(const char* type, const char* brand, const char* model, int year, int code, double price)

{

    resetInfo();

    setInfo(type, brand, model, year, code, price);

}

CarInventory::CarInventory(const char* type, const char* brand, const char* model)

{

    resetInfo();

    setInfo(type, brand, model, 2022, 100, 1);

}

CarInventory::~CarInventory()

{

    delete[] m_type;

    delete[] m_brand;

    delete[] m_model;

}

CarInventory& CarInventory::setInfo(const char* type, const char* brand, const char* model, int year, int code, double price)

{

    if (type == nullptr || brand == nullptr || model == nullptr || year < 1990 || code < 100 || price < 0)

    {

        resetInfo();

    }

    else

    {

        delete[] m_type;

        delete[] m_brand;

        delete[] m_model;

        m_type = new char[strlen(type) + 1];

        strcpy_s(m_type, sizeof(type), type);

        m_brand = new char[strlen(brand) + 1];

        strcpy_s(m_brand, sizeof(brand),  brand);

        m_model = new char[strlen(model) + 1];

        strcpy_s(m_model, sizeof(m_model),  model);

        m_year = year;

        m_code = code;

        m_price = price;

    }

    return *this;

}

bool CarInventory::isValid() const

{

    return m_type != nullptr && m_brand != nullptr && m_model != nullptr && m_year >= 1990 && m_code >= 100 && m_price >= 0;

}

void CarInventory::printInfo() const

{

    std::cout << "|" << std::setw(12) << m_type << "|" << std::setw(18) << m_brand << "|" << std::setw(18) << m_model << "|" << std::setw(6) << m_year << "|" << std::setw(6) << m_code << "|" << std::setw(11) << m_price << "|" << std::endl;

}

bool CarInventory::isSimilarTo(const CarInventory& car) const

{

    return m_type == car.m_type && m_brand == car.m_brand && m_model == car.m_model && m_year == car.m_year;

}

namespace sdds {

    bool find_similar(CarInventory car[], const int num_cars)

    {

        for (int i = 0; i < num_cars; i++)

        {

            for (int j = i + 1; j < num_cars; j++)

            {

                if (car[i].isSimilarTo(car[j]))

                {

                    return true;

                }

            }

        }

        return false;

    }
}

Header File

#ifndef CARINVENTORY_H
#define CARINVENTORY_H
#define _CRT_SECURE_NO_WARNINGS

namespace sdds {
class CarInventory {
    char* m_type;
    char* m_brand;
    char* m_model;
    int m_year;
    int m_code;
    double m_price;
    void resetInfo();
public:
    CarInventory();
    CarInventory(const char* type, const char* brand, const char* model, int year, int code, double price);
    CarInventory(const char* type, const char* brand, const char* model);
    bool isSimilarTo(const CarInventory& car) const;
    ~CarInventory();
    CarInventory& setInfo(const char* type, const char* brand, const char* model, int year, int code, double price);
    void printInfo() const;
    bool isValid() const;
    bool find_similar(CarInventory car[], const int num_cars);

  };
 }
    #endif

Test/main file

#include<iostream>
#include<iomanip>
#include "CarInventory.h"
#include "CarInventory.cpp"
using namespace std;
using namespace sdds;

 int main()
 {
const int num_cars = 6;
bool invalid_data = false;
CarInventory cars[num_cars] = {
    {},
    {"suv", "volvo", "xc90"},
    {"Truck", "Ford", "F 150", 2021, 105, 55000},
    {"Sedan", "BMW", "M550i", 2022, 101, 91000},
    {"Truck", "Tesla", "Cybertruck", 2021, 102, 65000},
    {"Sedan", "BMW", "M550i"}
};

if (cars[2].setInfo("SUV", "Volvo", "XC90", 2019, 109, 80000).isValid()) {
    cout << "Information was set correctly!" << endl;
}
else {
    cout << "Information was set incorrectly!" << endl;
}
if (cars[1].setInfo("SUV", "Volvo", "XC90", 1234, 1, 1).isValid()) {
    cout << "Information was set correctly!" << endl;
}
else {
    cout << "Information was set incorrectly!" << endl;
}


cout << setw(60) << "----- Car Inventory Information -----" << endl << endl;;
cout << "| Type       | Brand            | Model            | Year | Code |     Price |" << endl;
cout << "+------------+------------------+------------------+------+------+-----------+" << endl;
for (int i = 0; i < num_cars; i++) {
    if (cars[i].isValid())
        cars[i].printInfo();
    else
        invalid_data = true;
}

if (invalid_data) {
    cout << endl;
    cout << setfill('*') << setw(60) << "*" << endl;
    cout << "*  WARNING: There are invalid data in the inventory!      *" << endl;
    cout << setfill('*') << setw(60) << "*" << endl;
}
if (find_similar(cars, num_cars)) {
    cout << endl;
    cout << setfill('+') << setw(60) << "+" << endl;
    cout << "+  WARNING: There are similar entries in the inventory!   +" << endl;
    cout << setfill('+') << setw(60) << "+" << endl;
}
return 0;
  }

Compiler Error I've been getting

Answer 1

You need to remove #include "CarInventory.cpp" from your main.cpp file. It does not belong there.

Your project is already compiling CarInventory.cpp into CarInventory.obj and then linking that .obj into the final .exe . But you are asking the compiler to include all of CarInventory.cpp 's code into main.cpp 's code, which is compiled into main.obj . You are getting errors about all of CarInventory 's methods that are being duplicated in both .obj files.