CODEWITHSUNDEEP
c++classheader-files
Dustbin Saves you
Dustbin Saves you

Reputation: 126

While seperating classes, using a function in cpp file causes errors

So i just learned how to seperate classes and the youtube totourial is stressing on doing this alot, here's the link https://www.youtube.com/watch?v=NTip15BHVZc&list=PLAE85DE8440AA6B83&index=15 My code is the exact same as his, and in the cpp file theres this thing: mainClass::myfunction; (mainclass is the name of my class, myfunction is my function) when i try to execute my program, it gives an error:

unidentified reference to 'mainClass::myfunction()'

here's my main.cpp file code:

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

using namespace std;

int main()
{
    mainClass bo;
    bo.myfunction();
    return 0;
}

here's my mainclass.h code:

#ifndef MAINCLASS_H
#define MAINCLASS_H

class mainClass
{
    public:
        myfunction();
};

#endif // MAINCLASS_H

my mainclass.cpp:

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

using namespace std;

mainClass::myfunction()
{
    cout << "I am a banana" << endl;
}

I don't know much about these so could you just tell me what the errors here are, because i copied everything correctly from the guy's totourial but still it doesn't work P.S: this happens to me alot, i understand everything, nothing works, i copy everything, nothing works, and then i literally do exactly what the person is doing, still nothing works on all three of PC's, so i dont think the problem is with the devices lol

Upvotes: 1

Views: 38

Answers (1)

pepperjack
pepperjack

Reputation: 663

I doubt you completely copied and pasted that code because I'm fairly sure a teacher shouldn't be teaching having functions without a specified return type, but let's jump into it anyways...

Possibility #1 You meant to create a constructor for the class. In that case, please make sure the constructor function has the same name as the class. Also, you can't call it through .mainClass(), as it is a constructor.

class mainClass
{
    public:
        mainClass();
};
mainClass::mainClass()
{
    cout << "I am a banana" << endl;
}

Possibility #2 You meant to create the class member function myfunction. You really should be specifying what return type your function is of. Some compilers will auto-assume int return type, and so the function you created is int myfunction();, but you really should be specifying it as void myfunction(); since you didn't return anything. Addl. info: Does C++ allow default return types for functions?

Next, change how you are giving the definition, by adding the return type.

void mainClass::myfunction()
{
    cout << "I am a banana" << endl;
}

Possibility #3 Those should work, but another issue is that you might not have linked mainclass.cpp, so there is no definition available. In code blocks, right click on the project name and hit Add Files, then add the mainclass.cpp so the linker can define mainClass::myfunction().

To troubleshoot if the mainclass.cpp is being built with the project, try adding #error I'm included! to the file mainclass.cpp after #include "mainclass.h". If you get an error I'm included!, then it is linked and you can remove the #error.

Upvotes: 1

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