Question

I just created a Qt default project with a Qt designer form.

The class MainWindow is declared in a mainwindow.h and then included in mainwindows.cpp.

Why is it done this way ? Why not a declaration of this form directly in mainwindows.cpp ?:

class MainWindow
{
    ...
}

What is the proper way to add my code ? For example, a button that trigger a method.

Answer 1

In C++ you typically put class definitions into header files (.h), and method implementations in source files (.cpp). That allows clients of the class to use the class without having to see the implementation of each function. That also means that when adding a method, you’ll typically have to make two changes: add the method to the class definition (in the header) and then add the method’s implementation to the .CPP file.

In header file:

class MainWindow
{
    void SomeMethod();
};

In source file:

void MainWindow::SomeMethod()
{
    // Your code here.
}