[Qt-interest] Signal chaining

[Mandeep Sandhu]

On Mon, Mar 29, 2010 at 4:32 PM, Andre Somers <andre at familiesomers.nl> wrote:
> On 29-3-2010 12:47, Mandeep Sandhu wrote:
>> Hi All,
>>
>> I have a requirement where I need to send out a notification (as a
>> signal) to the user of my lib. The lib internally uses other helper
>> classes for getting the notification. These classes are not exposed
>> outside. All classes are QObjects.
>>
>> Eg: Class A (ext visible) --uses-->  Class B (internal) --uses-->Class
>> C (internal)
>>
>> One way is to emit signal from C, connect it to B, which in turn would
>> "re-emit"  it out to A, and so on (All signal-slot connections will be
>> direct (not queued) since it operates in a single thread's context).
>>
>> Would it be lighter to use simple callbacks? (but then I would need
>> the inner most class "C" to know about "A", since  finally A emits it
>> out to a "user")
>>
>> I'm running this in an embedded box and was worried about the overhead
>> of chaining these signals. If it's not much, I would prefer to use
>> signals.
>>
> How about just connecting the internal signals to the signals in the
> external API directly? You can connect signals to signals. There is no

Hmmm....it's nice to connect signal to signal. Those re-emitting slots
looked bad! :)

But for connecting signal of C to signal of A, I'll need to have C
visible in A (which I was trying to avoid, since C's something thats
for B's internal use! :)).

>From B to A the signal signature does change so i'll have to implement
a slot there.

Thanks,
-mandeep

> need for methods that do nothing else than re-emit a signal. Of course,
> that only works if the signatures are compatible.
>
> André
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