Qt-interest Archive, May 2007
Basic question in Signals and Slots
Message 1 in thread
Hi,
A basic question in QT ....
I have connected signal1 to slot1, signal2 to slot2, signal3 to slot3 and
signal4 to slot4.
signal1 is emitted and so slot1 is executed.
Within the slot1, I am emitting the other three signals.
slot1()
{
//do some stuff
emit signal2;
//do some stuff
emit signal3;
//do some stuff
emit signal4;
}
And the other slots are doing some simple stuff.
My Question is how the slots are executed. I have run a sample with just
print statements.
The control flow is ---> slot1() and in slot1 , after emitting the signal2
..... it is completing the stuff in slot2 and then the control comes to
next statement after emit signal2, then emits signal3 complets slot3 ,
emits signal4 complets slot4.
But I expect the slot1() will continue its execution after emitting
signal2 without waiting for slot2 to be completed.
Where I am gone wrong?
Thanks & Regards,
Hemanth Kumar Nakkina
Tata Consultancy Services
Mailto: hemanth.n@xxxxxxx
Website: http://www.tcs.com
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Message 2 in thread
Have a look at the docs:
http://doc.trolltech.com/4.2/signalsandslots.html
In most cases, a signal results in the corresponding slots to be called
immediatly. Don't mix them up with events!
Cheers,
Peter
> But I expect the slot1() will continue its execution after emitting
> signal2 without waiting for slot2 to be completed.
>
> Where I am gone wrong?
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Message 3 in thread
On 5/9/07, Hemanth N <hemanth.n@xxxxxxx> wrote:
> But I expect the slot1() will continue its execution after emitting signal2
> without waiting for slot2 to be completed.
>
> Where I am gone wrong?
That is because the connected slots are direct connected which means
execution will continue into those slots before returning to your
emit.
By using QueuedConnection on your slots, the signal is queued inside
Qt and emitted when control is back at Qt mainloop.
--
[ signature omitted ]
