Bug free programming with Qt:

ivan

While Qt is an excellent piece of software, and one of the most pleasant frameworks I've ever fell in love with, it has a fair share of bugs.

andre

I agree: Qt is good, but it not perfect and not nearly bug-free. It does however in most parts provide two IMHO very basic ingredients for making low-bug code:

It has a clear API (in part thanks to the guidelines Volker linked to) that makes it easy to use right, and hard to use wrong. That may sound trivial, but it is not. A good API encourages using it in such a way that it is hard to go wrong.

It has generally very good documentation. Good API documentation helps a lot. I frequently stumble on interesting looking libs or code, only to find the majority of the methods and classes are not or hardly documented. That makes using them a PITA.

CreMindES

Yes, it's a big help, I've read the gitorious version, and I will the trolltech too later.

I'm teaching simple C at the University for newbies in this year (I'm an electrical engineer student) and it's very important and quite hard sometimes to teach them how to correctly indentation and style their code. But I'm getting much nicer codes now from them :) So it's worth to tell it a hundred times :)

laurent bauer

Let's forget the "bug free" and rather talk about "robust" programming instead

So, good coding style and conventions contribute to "robust" programming. And we have several links.

Other possible Qt's contributors to "robust" programming may be:

signals & slots : for strong independency of components (+ impossible to crash even if bad coded ?)
Implicit sharing and associated objects with reference counting
Thread safe objects

Anything else ?

Panke

bq. (+ impossible to crash even if bad coded ?)

That your program does not crash, does not mean it has no bugs :-)

I agree to the other points though and think that the memory management things are most useful.

laurent bauer

What do you mean with "memory management things" ? The shared classes ?

Panke

[quote author="laurent bauer" date="1293645469"]

Implicit sharing and associated objects with reference counting
[/quote]

yes

laurent bauer

In the first post, i wrote: "You create an orphan widget, you attach it later to a parent widget. The parent takes ownership and you don’t need to worry anymore about the child life cycle"

I like this idea : you transfer the management of an object to an object owner. And you don't have to manage it yourself .

Do you know if this is a concept, a design pattern or anything which has a name?
Do you know if this coding way is described somewhere?

giesbert

The parent - child relationship, that includes lifetime coupling?

I would say it's a normal Komposition (UML :-) ).

laurent bauer

So simple? Well, I feel a bit ridiculous...

giesbert

Must everything be complicated?

ivan

In a sense, it is just an extension to the standard C++ behaviour to work with pointers (free on destruction) so it is not really a new concept.

laurent bauer

OK, I guess a widget has a container of children widgets which are destroyed by the parent destructor.
However, it must be a little bit more tricky because the ownership can be transfered to another parent widget.

goetz

It's only a QObjectList (which is just a typedef for QList<QObject *>). It is only little more than removing from one and inserting into the other list (and handling layout issues in case of widgets).

CreMindES

Yes, it's that simple :) The best things are so simple :)