Template <class T1, class T2, class T3> error LNK2019

Thanks for taking the time to read my post in advance.

I am using templates with classes and keep getting LINK error's from visual studio.net. The code is below.

Template.h

Code:

---

/* Vector.h
 * CS-260
 *
 * This file declares a class called Swap which
 * swaps the to variables passed by it.
 */

#include <iostream>
#include <cstring>
using namespace std;

//Base template that will swap the data of two variable passed to it
template <class T>
T swap(const T &a, const T &b)
{
        T temp;

        &temp = *&a;
        *&a = *&b;
        *&b = &temp;
}

//Specialized template that swaps variables of type char*
template <class T>
void swap(char*& first, char*& second)
{
        char *temp;
        strcpy(temp, first);
        strcpy(first, second);
        strcpy(second, temp);
}

//Class Tripple
template <class T1, class T2, class T3>
class Triple
{
private:
        T1 first;
        T2 second;
        T3 third;

public:
        //Constructors
        Triple();
        Triple(const T1 &a, const T2 &b, const T3 &c);

        //Destructor
        virtual ~Triple();

        //Accessors
        void setT1(Triple &lhs, T1 &rhs);
        void setT2(Triple &lhs, T2 &rhs);
        void setT3(Triple &lhs, T3 &rhs);

        //Operators
        friend ostream& operator<<(ostream& os, const Triple &rhs)
        {
                os << rhs.first << "\n"
                  << rhs.second << "\n"
                  << rhs.third << "\n";

                return os;
        }

};

---

Template.cpp

Code:

---

#include "Vector.h"

//Default Constructor
template <class T1, class T2, class T3>
Triple<T1, T2, T3>::Triple()
{
        first = NULL;
        second = NULL;
        third = NULL;
}

//Initial value contructor
template <class T1, class T2, class T3>
Triple<T1, T2, T3>::Triple(const T1 &a, const T2 &b, const T3 &c)
{
        first = a;
        second = b;
        third = c;
}

//Set member functions
template <class T1, class T2, class T3>
void Triple<T1, T2, T3>::setT1(Triple &lhs, T1 &rhs)
{
        lhs.first = T1;
}

template <class T1, class T2, class T3>
void Triple<T1, T2, T3>::setT2(Triple &lhs, T2 &rhs)
{
        lhs.second = T2;
}

template <class T1, class T2, class T3>
void Triple<T1, T2, T3>::setT3(Triple &lhs, T3 &rhs)
{
        lhs.third = T3;
}

---

Main.cpp

Code:

---

#include "Vector.h"

int main()
{
        //Test base class
        int age = 22;
        int income = 50000;

        //Print original values
        cout << "Age is " << age << "\n"
                << "Income is " << income << "\n\n";

        //Swap data of two variables passed
        swap(age, income);

        //Print new values
        cout << "Age is " << age << "\n"
                << "Income is " << income << "\n\n";

        // Test specialized class
        char *firstName = "Jonathan";
        char *lastName = "Antoine";

        //Print original values
        cout << "My first name is " << firstName << "\n"
                << "My last name is " << lastName << "\n\n";

        //Swap data of two variables passed
        swap(firstName, lastName);

        //Print new values
        cout << "My first name is " << firstName << "\n"
                << "My last name is " << lastName << "\n\n";

        //Test Triple Class Default constructor
        Triple<char*, int, char*> Address1;
        char *recipientName = "Jonathan Antoine";
        int houseNumber = 53070;
        char *streetName = "NW Manor Dr.";

        Address1.setT1(Address1, recipientName);
        Address1.setT2(Address1, houseNumber);
        Address1.setT3(Address1, streetName);

        Triple<char*, char*, int> Address2;
        char *city = "Scappoose";
        char *state = "OR";
        int zip = 97056;

        Address2.setT1(Address2, city);
        Address2.setT2(Address2, state);
        Address2.setT3(Address2, zip);

        cout << Address1 << "\n" << Address2 << "\n";
}

---

Thanks again in advance.

Put all the code in template.cpp into template.h.
Delete template.cpp.

Or rename template.cpp to template.hpp.
And put #include "template.hpp" at the bottom of template.h.

gg

Your swap template is incorrect.
Your char* template specialization of swap is incorrect (algorithmically).
You should put your swap implementations within their own namespace to avoid collision with std::swap.

gg

Ok. I have converted everything to template.h and am now getting only two errors. They are both the same and are listed below. Code is also shown.

Lab2 error LNK2019: unresolved external symbol "public: virtual __thiscall Triple<char *,char *,int>::~Triple<char *,char *,int>(void)" (??1?$Triple@PADPADH@@UAE@XZ) referenced in function _main

Template.h

Code:

---

/* Template.h
 * CS-260
 *
 * This file declares a class called Swap which
 * swaps the to variables passed by it.
 */

#include <iostream>
#include <cstring>
using namespace std;

//Base template that will swap the data of two variable passed to it
template <class T>
T swap(const T &a, const T &b)
{
        T temp;

        &temp = *&a;
        *&a = *&b;
        *&b = &temp;
}

//Specialized template that swaps variables of type char*
template <class T>
void swap(char*& first, char*& second)
{
        char *temp;
        strcpy(temp, first);
        strcpy(first, second);
        strcpy(second, temp);
}

//Class Tripple
template <class T1, class T2, class T3>
class Triple
{
private:
        T1 first;
        T2 second;
        T3 third;

public:
        //Constructors
        Triple();
        Triple(const T1 &a, const T2 &b, const T3 &c);

        //Destructor
        virtual ~Triple();

        //Accessors
        void setT1(Triple &lhs, T1 &rhs);
        void setT2(Triple &lhs, T2 &rhs);
        void setT3(Triple &lhs, T3 &rhs);

        //Operators
        friend ostream& operator<<(ostream& os, const Triple &rhs)
        {
                os << rhs.first << "\n"
                  << rhs.second << "\n"
                  << rhs.third << "\n";

                return os;
        }

};

//Default Constructor
template <class T1, class T2, class T3>
Triple<T1, T2, T3>::Triple()
{
        first = NULL;
        second = NULL;
        third = NULL;
}

//Initial value contructor
template <class T1, class T2, class T3>
Triple<T1, T2, T3>::Triple(const T1 &a, const T2 &b, const T3 &c)
{
        first = a;
        second = b;
        third = c;
}

//Set member functions
template <class T1, class T2, class T3>
void Triple<T1, T2, T3>::setT1(Triple &lhs, T1 &rhs)
{
        lhs.first = rhs;
}

template <class T1, class T2, class T3>
void Triple<T1, T2, T3>::setT2(Triple &lhs, T2 &rhs)
{
        lhs.second = rhs;
}

template <class T1, class T2, class T3>
void Triple<T1, T2, T3>::setT3(Triple &lhs, T3 &rhs)
{
        lhs.third = rhs;
}

---

Main.cpp

Code:

---

#include "Vector.h"

int main()
{
        //Test base class
        int age = 22;
        int income = 50000;

        //Print original values
        cout << "Age is " << age << "\n"
                << "Income is " << income << "\n\n";

        //Swap data of two variables passed
        swap(age, income);

        //Print new values
        cout << "Age is " << age << "\n"
                << "Income is " << income << "\n\n";

        // Test specialized class
        char *firstName = "Jonathan";
        char *lastName = "Antoine";

        //Print original values
        cout << "My first name is " << firstName << "\n"
                << "My last name is " << lastName << "\n\n";

        //Swap data of two variables passed
        swap(firstName, lastName);

        //Print new values
        cout << "My first name is " << firstName << "\n"
                << "My last name is " << lastName << "\n\n";

        //Test Triple Class Default constructor
        Triple<char*, int, char*> Address1;
        char *recipientName = "Jonathan Antoine";
        int houseNumber = 53070;
        char *streetName = "NW Manor Dr.";

        Address1.setT1(Address1, recipientName);
        Address1.setT2(Address1, houseNumber);
        Address1.setT3(Address1, streetName);

        Triple<char*, char*, int> Address2;
        char *city = "Scappoose";
        char *state = "OR";
        int zip = 97056;

        Address2.setT1(Address2, city);
        Address2.setT2(Address2, state);
        Address2.setT3(Address2, zip);

        cout << Address1 << "\n" << Address2 << "\n";
}

---

Thx for any help.

Firstly: int main()
Make sure you're returning a value at the end of your main function, return 0; does the trick.

The error seems to have something to do with the deconstructor of your class, which could, in turn, be linked to the above problem. Try adding this first and see what happens...

Added return 0;. Still getting same error.

>> ... unresolved external symbol ...
The linker can't find it - try to decipher what "it" is.

gg

Thanks all so much for the help. I did not have my deconstructor defined in my code. I only had it initialized.

Quote:

---

Originally Posted by Epo

Firstly: int main()
Make sure you're returning a value at the end of your main function, return 0; does the trick.

---

Not necessary, for the main function (only), the return statement can be left out and a return 0 will be assumed by most modern compilers.

>>*&a...
Just like to point out, *& is unneccessary. & takes address of, * finds value at address; combined, you end up with the same thing.

i.e. *&a is exactly the same as a :)