[Qt-interest] A new (?) const-correct way to create aUiobjectand do setupUi

[Niels Dekker (Qt-interest)]

>> I wouldn't mind if a function like createAndSetupUi would return a
>> non-const reference. Leaving it up to the user whether the ui member
>> variable is a const, or a non-const reference.

Robert Hairgrove wrote:
> But I thought that the whole motivation for this project was to provide
> a const UI object? We already have the non-const version...

The motivation is to *allow* the user to declare the ui member as a 
const reference, with only a *minimum* amount of boilerplate code. In 
that sense, I think my CreateAndSetupUi function does the job:

In the header file of the user's form:
   1. Forward-declare the Ui class.
   2. Declare the ui member as a const reference

And in the cpp file of the user's form:
   1. Include (#include) the definitions of CreateAndSetupUi and the Ui 
class.
   2. Initialize the ui member by CreateAndSetupUi(*this).

That's it. And FWIW, I think it's also more convenient to write e.g., 
"ui.pushButton" than "ui->pushButton".

> besides, I have yet to see the real benefit of having the
> UI member const. Who should change it? Either it is a private
> subclass or a private member variable (pointer or not).

I'm following Scott Meyers' recommendation to use const whenever 
possible (Effective C++ Third Edition, item 3). Even for private data. 
But of course, you are free to do otherwise.

However, I think a function like CreateAndSetupUi should not stop people 
from doing retranslateUi at any time (if necessary). Do I understand 
correctly that the call retranslateUi might as well be applied to a 
*copy* of the ui, while still having the same effect? For a ui of type 
UiClass, isn't ui.retranslateUi(this) equivalent to 
UiClass(ui).retranslateUi(this)?

Of course, a helper function (template) might be more convenient:

   template <class UiClass, class Parent>
   void RetranslateUi(UiClass uiParam, Parent& parent)
   {
     uiParam.retranslateUi(&parent);
   }

Allowing to do a retranslation of this->ui by RetranslateUi(ui, *this), 
even when ui is a const reference. Right?

Kind regards,

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