Class Constructor

a8wz

Could somebody please explain the syntax for this constructor, I mean what does it accomplish exactly. Sorry I am new to Qt and C++ and I've already read the docs but still need some clarification. As far as I understand MainWindow here declares QWidget as its parent, and the single column (":") is used for Initialization lists but I don't quite understand what this particular Initialization list does (especially the QMainWindow(parent) part, does it provide inheritance for MainWindow from QMainWindow class?). Thanks in advance.

@MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent), ui(new Ui::MainWindow)@

SGaist

Hi,

@
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent) << call base class constructor passing parent
, ui(new Ui::MainWindow) << instanciate a new Ui::MainWindow object and assign it to the ui variable (well assign the pointer to the newly created object to ui which is a pointer to a Ui::MainWindow object)@

Hope it helps

a8wz

Thank you, it did, but can you also please tell me why it is needed.

Chris Kawa

Simple example :
@
class A {
A() { ... }
A(Type param) { ... }
};

class B : public A {
B(Type param) {} //this will call A() implicitly
B(Type param) : A(param) {} //this will call A(param)
};
@
So it's needed to pass the parent pointer to the base class QObject so that it can do its magic with it. Otherwise the parent parameter would be ignored.

Solved Class Constructor