Thread: Function outside the CLass

An undefined reference usually means that you have a declaration:

Code:

void do_something();

but no definition:

Code:

void do_something()
{
  std::cout << "Doing something!" << std::endl;
}

Or in other words, the functions( aka the methods of the class ) aren't properly defined. Consider this example:
MyClass.h

Code:

class MyClass
{
    public:
        MyClass();
        ~MyClass();

        int getValue() const;
        void setValue(int newVal);

    private:
        int value;
};

MyClass.cpp

Code:

MyClass::MyClass(): value(0) {}
MyClass::~MyClass() {}

int MyClass::getValue() const { return value; }
void MyClass::setValue(int newVal) { value = newVal; }

It can also mean you did not compile all .cpp files.