Constructor will run but not function from other file - c++

Question

Sorry new to C++ here and cannot find the answers that I am looking for anywhere. I am trying to run the simplest possible program in C++ using OOP and multiple files. If the Vehicle class has no doSomething() function in it, then the constructor prints out just fine. When I add the function and call car.doSomething() it just gives me errors. I have searched for days and can't find a working answer.
main.cpp
#include <stdio.h>
#include <iostream>
#include "Vehicle.h"
using namespace std;
int main(int argc, char **argv){
Vehicle car;
car.doSomething();
return 0;
}
Vehicle.cpp
#include "Vehicle.h"
Vehicle::Vehicle(){
cout << "do something" << endl;
}
void doSomething(){
cout << "do something else" << endl;
}
Vehicle.h
#pragma once
#include <iostream>
using namespace std;
class Vehicle{
public:
Vehicle();
void doSomething();
};
Like I said, new to C++ and not sure how to fix this. Thanks for any help.
Specs:
Codelite v10.0.0,
Linux Ubuntu 18.04
Error: undefined reference to 'Vehicle::doSomething()'

Answer 1

You didn't need to search for days; you only needed to read the chapter in your C++ book about defining member functions.
It goes like this:
void Vehicle::doSomething()
{
cout << "do something else" << endl;
}
That Vehicle:: is how the computer knows that this doSomething definition is for the class Vehicle (just like you did already with the constructor).
Without that, it's just an ordinary function. It doesn't matter that the file is called Vehicle.cpp; C++ doesn't really care about filenames. You could have all sorts of functions, variables, class definitions etc in that file, regardless of whether it were called Vehicle.cpp or Stuff.cpp or Lightness4Eva.cpp (that's not to say that your naming convention is ungood, though!).

Answer 2

I suppose you have "unresolved" linker error in this case. It means error is not in runtime but in build time. Error message could prompt you that linker can't find Vehicle::doSomething(). This would point you that you didn't actually provide doSomething() function. Read error outputs, it helps to understand what is wrong.

Answer 3

write doSomting() defination with class name as in .cpp file:
void Vehicle::doSomething()
{
cout << "do something else" << endl;
}