Undefined reference to header file function

Question

I got an error of C:\temp\hashTableProject\main.cpp|14|undefined reference to hash::Hash(std::string) Anyone know how to solve this problem?

hash.h

#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;

#ifndef HASH_H
#define HASH_H

class hash{
public:

    int Hash(string key);
};

#endif // HASH_H

hash.cpp

#include <iostream>
#include <cstdlib>
#include <string>

#include "hash.h"

using namespace std;


int hash::Hash(string key){

    //int hash = 0;
    int index;
    index = key.length();

    return index;
}

main.cpp

#include <iostream>
#include <cstdlib>
#include <string>

#include "hash.h"

using namespace std;

int main()
{
    int index;
    hash hashOb;
    string traget = "Testing";
    index = hashOb.Hash(traget);

    cout << index << endl;

    return 0;
}

Im using CodeBlock 13.12 There is only main.o file in obj folder. I dont know why the hash.o isn't there.

Answer 1

hash is an inbuilt template in "std" namespace.

Try removing using namespace std; lien and use namespace name as and when required.