Question

When I try to compile this code

Analysis2::Analysis2() //line 13
{
    Seconds_v = 0;    //Seconds_v and Seconds_t are both of type int 
    Seconds_t = 0;    //and declared in header
}

I get this error

analysis2.cpp:13: undefined reference to `FileParameters::FileParameters()’

Why is it giving me that undefined reference? FileParameters is a class included in Analysis2 and there is a FileParameters object defined in the Analysis2 header file if that helps.

Answer 1

When you have constructor, every member variable is automatically default-constructed if you don’t explicitly construct it in the initializer list. Your code above automatically expands to:

Analysis2::Analysis2() : mFileParams(), Seconds_v(), Seconds_t() // line 13
{
    Seconds_v = 0;    //Seconds_v and Seconds_t are both of type int 
    Seconds_t = 0;    //and declared in header
}

And if you didn’t implement the default constructor of FileParameters yet, or don’t even have an accessible one, that’s the error you get.