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How different is Qt4 from Qt3?

I used to program in Qt3, and I read a great book that I still have O'reilly on Qt3. I wanted to start using Qt4 again a few years later.

Can I use my Qt3 book to get back on track, or has everything changed so much that I have to buy a Qt4 book?

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c ++ qt qt4
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8 answers

In a nutshell:

  • Qt 4 (even) is better - and more powerful and flexible - than Qt 3
  • everything will be fine!

Porting to the Qt 4 documentation provides some insight into many small API changes.

What's New in Qt 4 gives an overview of the big differences between Qt 3 and Qt 4.

Some important changes that no one has mentioned:

  • Model / View Architecture
  • template container classes
  • new, modular assembly system
  • new action-based main window implementation
  • CSS widget style
  • Ports for S60 and other platforms.

There are also many small fixes, enhancements, and useful new classes, such as QFormLayout and QSignalSpy.

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You should consult the Qt books page on Nokia.

Two books from this page are freely available:

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Qt3 support classes still exist in Qt4, but Qt has evolved a lot. I think using your Qt3 book will slow you down. It’s best to buy a new book.

If you don’t want to spend money on a book, examples, tutorials, and documentation are very useful.

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You can find a document from 3 to 4 manuals with all the differences of the Nokia website .

I would recommend the Qt 4 book for Qt 3, but since you've already worked with Qt, I think you can just use the docs and be fine.

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Most things remain very similar. There was some cleaning, but the basics (signal-slot mechanism, for example) remained the same. You still have QStrings, QActions, QDialogs, etc. Knowledge of Qt3 should remain valuable.

On the other hand, there are many new elements. There is a large QGraphicsView infrastructure, Phonon framework for multimedia files, QtWebKit HTML engine, QtConcurrent mechanism for multithreading, etc. You might want to learn all new goodies.

Trolltech (what is the current name?) Always has good documentation, so check What's New in Qt4 and you'll be fine with the API Link for the latest version of Qt4.

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If you know Qt, this http://qt.nokia.com/doc/4.5/classes.html should be good to adapt.

To redirect to the documentation for the latest version of Qt, use one of the following links: http://doc.trolltech.com/latest/ or http://qt.nokia.com/doc/latest/

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I say that you have been using the constructor for a while and look at the generated code. I used it to learn how to work with Qt4.

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Qt4 is much more powerful than Qt3 (especially now that Qt 4.6 is approaching, although Qt 4.0 had some flaws). Your knowledge of Qt3 will allow you to do basic things with Qt4, as the style has not changed much for the basic functions, but in order to really use the full power of Qt4, you will need to learn things specific to Qt4.

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