[Qt-interest] inheritance problem

[Eirik Ulvik]

Why don't you create separate QWidget based classes that can be inserted 
into the respective tabs of the QTabWidget? You can use signals/slots 
for communcation between the different parts of the UI.

Eirik

Den 26.02.2010 12:49, skrev franki:
> Thursday 25 of February 2010 23:57:00 Malyushytsky, Alex napisał(a):
>    
>> You derive from the class you need to derive from.
>>
>> If I understood your problem (which I am not sure) you want  to use your
>> derived class instead of QTabWidget. In this case you might use "Promoting
>> Widgets" technique.
>> http://doc.trolltech.com/4.6/designer-using-custom-widgets.html
>>      
> Hi,
>
> I've read about promoting widgets and I think it's not what I need.
> Maybe I explain it in different words:
> The way I'm doing my application now is called: "The Single Inheritance
> Approach", so in my case QTabWidget is placeholder for all widgets that
> constitute the user interface.
> Next, I sublassed this QTabWidget with my class custPanel_TabWidget
> and the header file is like this:
>
> #include "ui_custpanel.h"
> class custPanel_TabWidget: public QTabWidget
> {
> 	Q_OBJECT
> public:
> 	custPanel_TabWidget ();
> 	~custPanel_TabWidget();
> 	Ui::custPanel_TabWidget cp;
> }
>
> so now all widgets created inside QTabWidget (by Qt Designer) are accessible
> by this variable "cp", and when I need to connect some signals, genrated for
> example by pushButtons, with functions inside custPanel_TabWidget then it is
> simple as that:
> connect(cp.saveButton,SIGNAL(clicked()),this,SLOT(saveValues()))
>
> But the problem is, that I have lets say 10 tabs in QTabWidget (each tab
> present some different data for user, and each use different functions to
> manage this data) and all these functions are inside class
> custPanel_TabWidget - so this file has grown big, and does not look clean.
>
> So I thought about creating class for each tab, and that class should maintain
> functions needed to interact with user.
> Now is what I'm not sure:
> As I understand this now, if I subclass from class custPanel_TabWidget I will
> be able to access "cp" variable (which means easy access to all widgets in
> QTabWidget just like this->cp), and I will be able to access all public
> functions created inside custPanel_TabWidget, so the inheritance model would
> look like this
> QTabWidget ->  custPanel_TabWidget ->classForTab1
>
> But when I'm trying to create class that subclass from custPanel_TabWidget I
> get this error:
> invalid use of incomplete type 'struct custPanel_TabWidget'
>
> and the header is like this:
>
> #include "custpanel.h"
> class custPanel_TabWidget;
>
> class classForTab1: public custPanel_TabWidget
> {
> public:
>          classForTab1 ();
>          ~classForTab1();
> };
>
> So are there some mistakes in what I think I know about inheriting from other
> classes, and how to make this class "classForTab1"
>
> The second apporoach that I mentioned in previous post, was to create new
> class and pass it variables like "cp" (to access widgets inside QTabWidget)
> and others - to access objects holding connection to sql, and finally pointer
> to the base class (custPanel_TabWidget)
> So the constructor for classForTab1 looks like this:
> classForTab1::classForTab1(Ui::custPanel_TabWidget cp,ItSql *itsql,QVariant
> cust_id,custPanel_TabWidget *parent) : QWidget ()
>
> It works fine, but it does not look clean.
> So please help.
>
> Greetings
> Marek
>
>    
>> In your case:
>>
>> - You subclass from the QTabWidget
>> - in designer place QTabWidget and then promote it.
>>
>> Hope this helps,
>>     Alex
>>
>>
>>
>> -----Original Message-----
>> From: qt-interest-bounces at trolltech.com
>> [mailto:qt-interest-bounces at trolltech.com] On Behalf Of franki Sent:
>> Thursday, February 25, 2010 8:11 AM
>> To: qt-interest at trolltech.com
>> Subject: [Qt-interest] inheritance problem
>>
>> Hi,
>>
>> I've application with QMainWindow and tabWidget as a centralWidget,
>> class that maintains this tabWidget is called custPanel_TabWidget
>> some piece of custpanel.h:
>>
>> #ifndef CUSTPANEL_H
>> #define CUSTPANEL_H
>> #include "ui_custpanel.h"
>>
>> class custPanel_TabWidget: public QTabWidget
>> {
>>          Q_OBJECT
>> public:
>>          custPanel_TabWidget (QWidget *parent,QVariant cust_id,ItSql
>> *itsql); ~custPanel_TabWidget();
>>          Ui::custPanel_TabWidget cp;
>> }
>>
>> I wanted each tab to be maintained by its own class, because there is so
>> many functions that custPanel_TabWidget started to be huge mess.
>> so I did class e.g. Notify
>> header notify.h:
>>
>> #ifndef NOTIFY_H
>> #define NOTIFY_H
>> #include<QObject>
>> #include "custpanel.h"
>>
>> class custPanel_TabWidget;
>>
>> class Notify: public custPanel_TabWidget
>> {
>> public:
>>          Notify ();
>>          ~Notify();
>> };
>>
>> but during compilation, I get error:
>> invalid use of incomplete type 'struct custPanel_TabWidget'
>>
>> I've googled somewhere that I should derive from Ui::custPanel_TabWidget
>> instead of custPanel_TabWidget, because this class is called that way in
>> ui_custpanel.h - which is true.
>> But, when I've tried to derive from Ui::custPanel_TabWidget, program
>> compile fine, but I can't access any widget on tabWidget, and in fact which
>> class do I derive from?
>>
>> Second sollution for me, that I've proven to work earlier, was to pass some
>> variables to new class instead of deriving from custPanel_TabWindow, and
>> maintain all function related to this tab in that new class.
>> So in that case, the constructor is like this:
>>
>> Abonament::Abonament(Ui::custPanel_TabWidget cp,ItSql *itsql,QVariant
>> cust_id,custPanel_TabWidget *parent) : QWidget ()
>>
>> And this second approach works fine for me, but which one is better, or
>> which one is recommended?
>>
>> Thanks in advance
>> Marek
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