Is there way to use QT Designer UI forms so you get direct access to the form widgets in your program?

Crag_Hack · wrote on 13 May 2016, 20:06

I'm having trouble finding a way to use multiple UI forms in one program so that I get direct access to the widgets in the forms. Direct access would make it much easier to implement my backend and connect it the frontend form files. As it is now I have to use public modification methods to change widgets in the forms and also intermediate signals and slots to communicate between the form's widgets and the code in my backend class. It would be much easier to just change the widgets directly and connect them directly to slots in my backend class. Can something like this even be done? Thanks

SGaist · wrote on 13 May 2016, 20:29

Hi,

Yes it might be done but it's the first step to tight coupling and maintenance nightmare (you don't want either for them).

How are you implementing your backend ?

Crag_Hack · wrote on 13 May 2016, 21:09

I just created a QT Creator project with .cpp/.h. Then for the forms I added QT Designer Form Classes for each one. It's just a nightmare to have to do everything without direct access. Choose your nightmare perhaps? :) Any ideas to make things easier?

SGaist · wrote on 13 May 2016, 21:54

That's why I asked about the backend implementation ;)

Your widgets should be responsible for connecting to the backend so one way to do that is to add a setupBackend method to them and in there do all the connection needed. Doing so you have access directly to said widget internal details thus if you modify it, you only have to change code within that widget. This keeps your code clean and easy to maintain.

Crag_Hack · wrote on 14 May 2016, 00:09

You're talking about my form top level widgets right? So I just add the method to the form class? How do I connect signals and slots between the form and the backend then? Also curious about your mention of the possibility of direct access in the first reply - can you elaborate a little?
Thanks again

SGaist · wrote on 14 May 2016, 19:37

I mean any widgets you build that would need a connection to your backend.

You do the connections in that method i.e.:

void MyCoolWidget::setupBackend(MyCoolBackend *backend)
{
    connect(backend, &MyCoolBackend::stringBasedSignal, ui->statusLabel, &QLabel::setText);
    // etc.
}

That way all the code stays in MyCoolWidget and if you change that class e.g. you replace the QLabel by a QLineEdit, you only have to modify setupBackend. No need to hunt every line where you could have done a connection between MyCoolWidget and MyCoolBackend.

You can give access to the ui variable from your widgets. Again, I very strongly advice to not do such a thing.

Crag_Hack · wrote on 15 May 2016, 19:07

What if I have to go the other way around? - click a button on a widget and do some backend stuff. Also as you probably figured out I'm a newbie to all this stuff. I have a background in data structures and basic programming and inheritance etc... - I'm basically an intermediate level programmer. Can you recommend any books or tutorials to help me out with this scenario of backend vs fronted and ui forms specifcally QT? Thanks :)

SGaist · wrote on 15 May 2016, 20:58

Same principle:

void MyCoolWidget::setupBackend(MyCoolBackend *backend)
{
    connect(backend, &MyCoolBackend::stringBasedSignal, ui->statusLabel, &QLabel::setText);
    connect(ui->startButton, &QPushButton::clicked, backend, &MyCoolBackend::igniteToaster);
    // etc.
}

This book might be of interest. Look for the parts about the Façade pattern.

Crag_Hack · 16 May 2016, 08:13

If I were to read one QT book... which would you suggest? :) The same? Perhaps just the Facade pattern then another book? I'll stop bugging you now ...

mrjj · wrote on 16 May 2016, 08:13

@Crag_Hack
Hi
When i started with Qt, i like to browse around in this one
http://www.bogotobogo.com/cplusplus/files/c-gui-programming-with-qt-4-2ndedition.pdf
I find it goes well with Qt docs to learn about different classes and ways to structure the app.

Crag_Hack · wrote on 18 May 2016, 20:54

Do either of those books cover how to make graphical renditions of widgets like special cool looking buttons and windows etc? Thanks. That's all folks!

SGaist · wrote on 18 May 2016, 21:56

What kind of special cool looking buttons do you have in mind ?

Crag_Hack · wrote on 19 May 2016, 05:47

These are a good example... just general graphic design for guis.
samsung ssd magician
mozy

Crag_Hack · wrote on 19 May 2016, 05:52

It does appear deceptively complicated to me initially but upon second look actually looks kinda simple :) toughest part being developing an eye for such things

SGaist · wrote on 19 May 2016, 21:21

For the first one I'd recommend going with QtQuick, that will be easier to build. The second can be accomplished with widgets with some styling but again, you'll likely be faster with QtQuick to do it.

Crag_Hack · wrote on 19 May 2016, 23:46

I'd rather not use QT Quick unless it's necessary because I'm not familiar with it. Maybe I should bite the bullet and learn it... With widgets though do those books teach you how to do gradients / style sheets / icons and graphics etc so you can make great looking programs? Also if QT Quick is super easier and more effective can I integrate with my C++ backend?