C++ Why can't I call a funtion in my class

Question

How can I get this code to work?

main.cpp

#include <iostream>
#include "TestClass.h"

using namespace std;

int main()
{
TestClass testclass;
int number = testclass.AddNumbers(3, 5);

cout << number << endl;
return 0;
}

TestClass.h

#ifndef TESTCLASS_H
#define TESTCLASS_H 


class TestClass
{
    public:
        TestClass();
        int AddNumbers(int num1, int num2);
    protected:
    private:
};

#endif // TESTCLASS_H

TestClass.cpp

#include "TestClass.h"

TestClass::TestClass(){

}

int TestClass::AddNumbers(int num1, int num2){
    return num1 + num2;
}

The only error I get is "Undefined reference to TestClass::TestClass() and "Undefined reference to TestClass::AddNumbers(int, int)".

How are you compiling this? Are you sure TestClass.cpp was compiled ? — jpo38, Oct 21 '14 at 18:46
Most likely you have not added TestClass.cpp to your project. — drescherjm, Oct 21 '14 at 18:46

Zuppa · Answer 1 · 2014-10-21T19:02:23.473

2

When you're compiling two .cpp files, you will get as a result two "object files". These are intermediate files containing the compiled content. After that, you need to link them to the actual executable binary.

Have a look at the link Captain Oblivous provided and check out the second answer. It explains this in greater deep.

edited Oct 21 '14 at 19:02

answered Oct 21 '14 at 18:45

Zuppa

467
5
16

I really don't understand this answer. I'm very new to c++ and I'm working in Code::Blocks so I don't know what settings I would have to change for this to work. – Nobodyknows2202 Oct 21 '14 at 18:57
Check that both .cpp files are in the actual project, so Code::Blocks will link them. – Zuppa Oct 21 '14 at 19:04
I added them twice, and it still did not compile. Is my code wrong in any way? – Nobodyknows2202 Oct 21 '14 at 19:11
***Is my code wrong in any way?*** Your code does not look wrong to me. – drescherjm Oct 21 '14 at 19:26
Your code is not wrong, but your project is, since it seems not to link the generated code of Testclass.cpp. Check your project settings. – Zuppa Oct 22 '14 at 11:29

C++ Why can't I call a funtion in my class

1 Answers1