[Qt-interest] A new (?) const-correct way to create a Ui object and do setupUi

[Niels Dekker (Qt-interest)]

There are various ways to use the Ui class generated by the User Interface 
Compiler (uic), as described at 
http://doc.qt.nokia.com/4.7-snapshot/designer-using-a-ui-file.html 
Personally, I find the approach that has a Ui object as member variable the 
most intuitive one:

  #include "ui_calculatorform.h"

  class CalculatorForm : public QWidget
  {
    ...
    Ui::CalculatorForm ui;
  };

However, this approach causes extra header file dependencies. So 
doc.qt.nokia.com also presents an alternative, removing the #include 
"ui_calculatorform.h" from the header file, and declaring the Ui member 
variable as a pointer. I certainly find this an interesting alternative. But 
instead of a pointer, I'd rather have a reference. Or even better: a const 
reference! Protecting the Ui object against any accidental modifications! It 
took me some time to figure out a convenient way to support declaring the Ui 
member variable as a const reference. But I think I got it working now, by 
introducing a template function, CreateAndSetupUi(T&). To be used as 
follows:

  class CalculatorForm : public QWidget
  {
    ...
    const Ui::CalculatorForm& ui;
  };

  CalculatorForm::CalculatorForm(QWidget *parent)
     : QWidget(parent),
      ui( CreateAndSetupUi(*this) )
  {
  }

Note that the ui reference does not need to be deleted. (It cannot even be 
deleted, of course, because it is not a pointer!) The argument of 
CreateAndSetupUi(T&) is used as parent of the newly created Ui object, so it 
will take care of deallocation. Internally, the argument is also passed to 
setupUi.

Actually the template function does not really return a reference to the 
created Ui object. It returns a proxy object, which converts implicitly to a 
(const) reference of the right Ui class type.

Is this idea of interest to anyone else here? I wouldn't mind sharing the 
implementation of CreateAndSetupUi. But I'm also interested to hear if such 
an approach is already presented elsewhere.

Kind regards, Niels
--
Niels Dekker
http://www.xs4all.nl/~nd/dekkerware
Scientific programmer at LKEB, Leiden University Medical Center