[Interest] A suggestion about replacing signals, actions and slots

[André Somers]

Op 27-12-2012 15:35, Oleg Yarigin schreef:
> Hello,
>
> I read http://byuu.org/articles/qt and got a question, why Qt uses slots and signals?
That blog is outdated, incomplete and biased. I am not claiming Qt is 
without bugs, but...
>   That stuff can be safe replaced with function pointers. I am sure, it can give some advantages.
Such as? Big claims require big evidence, and you're offering none.
>
> For instance, for now we need to use something like this to connect callbacks (actions):
>
> 	connect( <a>, <a`s action>, <b>, <b`s slot> );
>
> then we use moc, Q_OBJECT macro and special "slots:" class section.
There is nothing special about 'slots:' or 'signals:' or even 'emit'. 
You don't even need to use them if you don't want to. Use Q_SLOT or 
Q_SIGNAL instead if you prefer, and if you want, you can leave out the 
emit completely.
>
> I hope, this stuff can be better (with a way below we do not need to use moc, qmake and have an overhead in Qt library):
>
>
> What do you think about it? If you are agree, I will create a new brunch in Qt repo for making these changes.
You clearly have no clue what you're talking about. First of all, you 
*can* use function pointers (instead of slots) now for your connections. 
And yes, that includes lambda functions. Second, moc and Q_OBJECT does a 
good deal more than just dealing with signals and slots.

3rd, Qt's signals and slots do a lot more than a vanilla function 
pointer will ever do. Or can that transparently handle threading? Queued 
connections, blocking if needed? Type safety? Provide information on who 
triggered the signal? Work with mis-matched argument lists? Work with 
signal-signal connections? Provide many-to-many relationships between 
the caller (signal) and the callee (slot)? Signals & slots do provide 
all that.

Other toolkits have also seen all this value, and actually copied the 
concept. Boost for instance: 
http://www.boost.org/doc/libs/1_52_0/doc/html/signals.html But most of 
Qt's implementation was already working just fine long before the 
advanced template stuff needed for boost to work was broadly available...

André