From: Stefano Crocco <stefano.crocco@...>
Date: 2010-08-17T03:23:45+09:00
Subject: Re: QtRuby : constructor optional parameter

On Monday 16 August 2010, Arturo Bonechi wrote:
> |Hello everyone!
> |
> |I would like to know how to manage (with QtRuby) the optional parameter
> |from the constructor of a lot of classes (in Qt C++).
> |
> |I join a quick example.
> |
> |Thank you!
> |
> |Here is the code:
> |
> |require "Qt4"
> |
> |class Tree < Qt::TreeWidget
> |  def initialize parent # = 0 ??? (or something like that)
> |                        # because I want this parameter to be
> |                        # optional like in the parent class
> |    super parent
> |  end
> |end
> |
> |class Window < Qt::MainWindow
> |  def initialize
> |    super
> |
> |    # I have to use self whereas I want NO parameter
> |    setCentralWidget Tree.new self
> |  end
> |end
> |
> |if __FILE__ == $0
> |  a = Qt::Application.new ARGV
> |
> |  g = Window.new
> |  g.show
> |
> |  a.exec
> |end

Use nil as default value. Generally speaking, everywhere the C++ takes a 
QObject* or QWidget* parameter which can be 0, with qtruby you can pass nil. 
So, the initialize method of your Tree class would be:

class Tree < Qt::TreeWidget

  def initialize parent = nil
    super
  end

end

Note that you don't need to pass any argument to super: calling it without 
arguments automatically passes it all the arguments passed to the overridden 
method.

I hope this helps

Stefano