[Qt-interest] Question SLOT Macro & messing with the QObject::connect method

[Jefferson Bandeira]

Have you tried passing SLOT(handleMenuItems()) as an argument insteaf of
"handleMenuItems()"?

2010/2/4 kent williams <nkwmailinglists at gmail.com>

> I just have the habit of turning any block of code I need to use over
> and over again into a convenience function.  I'd think EVERYONE would
> want to have that habit, but when I read other people's code it sure
> seems like they're a lot more excited by Cut & Paste in their editor
> than they are about functional decomposition as a programming
> technique.
>
> Anyway Creating menus is one of those things I do more than once, so I
> made it a function.
>
> So in my code I have something like this:
>
> QMenu *menu = new QMenu(this); // this being the main window of the
> application
> const char *items[] = { "First Item", "Second Item", "Third Item", 0 };
> this->MakeMenu(menu, "handleMenuItems()", items);
>
> I COULD create actions one at a time and add them to the menu, but in
> this case, I just have to write 3 lines of code. Plus, if I want to
> change something about how my menus are constructed, I only have to
> fix the MakeMenu method, not change the code every place I make a
> menu.
>
> What it really boils down to is this: Qt defines this method for QObject:
> bool QObject::connect( const QObject * sender,
>                                  const char * signal,
>                                  const QObject * receiver,
>                                  const char * method,
>                                  Qt::ConnectionType type =
> Qt::AutoConnection );
>
> But the strings for the parameter signal and method encode their type
> with a prepended '1', '2', or '3'.  Now I've been programming
> computers since 1983, I really have no trouble prepending a digit on
> my signal/slot string.  What I was asking is this:
>
> Is there a better way to do this that is more consistent with the
> spirit of Qt, or did the Qt authors figure people would just read the
> headers and hack it together the way I did?
>
> On Thu, Feb 4, 2010 at 1:19 PM, Jefferson Bandeira <jbsilva at ufrj.br>
> wrote:
> > I really can't see what exactly you're trying to do with that piece of
> code,
> > are you trying to introduce Custom Slots at runtime? 'Cause i think it's
> not
> > supported at all, if it's not this, could you clarify a bit what exactly
> are
> > you trying to do?
> >
> > 2010/2/4 kent williams <nkwmailinglists at gmail.com>
> >>
> >> I don't think you understand what Slot does.
> >>
> >> #define SLOT(a) "1"#a
> >>
> >> # is the preprocessor 'stringify' operation.  It takes the argument
> >> and turns it into a string literal. For example
> >> SLOT(kickme())
> >>
> >> is turned by the C Preprocessor into
> >>
> >> "1" "kickme()"
> >>
> >> and since adjacent string literals are merged, it will become
> >>
> >> "1kickme()"
> >>
> >> So you can _ONLY_ use the SLOT macro at compile time.
> >>
> >> At runtime, say, if you want to stick a bunch of boilerplate Qt code
> >> into a convenience function, you just can't use SLOT(), because
> >> there's no way to go from a passed const char * parameter back to a
> >> string literal to use for a SLOT parameter.  You  can fake it -- which
> >> is what I do -- create a string at runtime with a literal '1'
> >> prepended.
> >>
> >> The problem, as I see it, is that with respect to proper C++ the
> >> SIGNAL/SLOT/METHOD business is stuck in the compile-time realm, even
> >> the the whole POINT of Qt's Signals and Slots paradigm is that the
> >> connections between signals and slots happen at runtime!
> >>
> >>
> >> On Thu, Feb 4, 2010 at 11:17 AM, Ian Thomson <Ian.Thomson at iongeo.com>
> >> wrote:
> >> > Hi,
> >> >
> >> > kent williams wrote:
> >> >>
> >> >> So my question is this: is there a non-evil way to get around SLOT()
> >> >> requiring a string literal instead of a char * variable?
> >> >
> >> > Isn't the const char* you're talking about a literal somewhere else in
> >> > your
> >> > program? Call SLOT() on it there.
> >> >
> >> >
> >> > Cheers,
> >> > Ian.
> >> >
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> >
> >
> >
> > --
> > Jefferson Bandeira
> >
> >
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> >
> >
>
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-- 
Jefferson Bandeira
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