From: Stefano Crocco <stefano.crocco@...>
Date: 2010-11-21T22:35:49+09:00
Subject: Re: Qt-Ruby implementation of the "Address Book Example"

On Sunday 21 November 2010 21:20:37 Arturo Bonechi wrote:

> Thank you for the reply!
>
> Stefano Crocco wrote in post #962907:

> > I'm not completely sure, but this should work:
> > - define a method called add_entry which takes two optional arguments
> > having
> > nil as default value. Inside the method, you check whether one of the
> > arguments is nil or not and choose the correct behaviour accordingly:
> >
> > def add_entry name = nil, address = nil
> >
> >   if name and address
> >
> >     #behave as the addEntry(QString, QString) function
> >
> >   else
> >
> >     #behave as the addEntry() function
> >
> >   end
> >
> > end

>
> Indeed, it works! The simplest solution is often the better! Thank you!
>

> > - define two slots, one with no arguments and one with two arguments:
> >
> > slots 'add_entry()', 'add_entry(QString,QString)'

>
> By the way, I have some questions again.
> - In this example, they use the QPair class. It seems that this class
> isn't implemented in Qt-Ruby (as for the array and hash classes). So I
> use an array of size two instead and it seems to work fine. Is it the
> way to do it or do I have to use an other Ruby class to use QPair?
Yes, using an array here is correct. Everytime you see a collection
looking
like a list in C++ (for example, whenever they use QStringList), you
need to
replace it with an array in qtruby

> - If I want to create a slot that have a Ruby hash as parameter, which
> QT class must I use in the slot declaration (QHash, QMap, ...)?
>

I don't think you can do that. It seems that neither QHash nor QMap are
implemented in qtruby, and passing a native ruby hash doesn't seem to
work. In my opinion, being restricted to using C++ types is one of the
most serious weaknesses of qtruby. In your case, I think the best option
would be to declare both signal with a string argument, then convert the
hash to a string (using Marshal or YAML) before emitting the signal and
converting it back in the slot.

> > Note that this won't work with signals: there can be only one signal
> > with a
> > given name, regardless of its signature.

>
> I didn't knew that, thank you. Is it specific to Qt-Ruby or it is the
> same in C++?

No, it's another limitation of qtruby. It's caused by the fact that
calling
signals creates a method taking a number of parameters according to the
signature you specified. Calling it again with the same name attempts to
create another method with the same name and (maybe) a different number
of
arguments. Since ruby doesn't allow to have different methods with the
same
name, however, this effectively overwrites the first method.

Stefano

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