Qt new style signals/slots

Willem Ferguson willemferguson at zoology.up.ac.za
Sat Jan 18 21:32:43 PST 2020

On 2020/01/18 21:32, Dirk Hohndel wrote:
> Hi Willem,
>> On Jan 18, 2020, at 3:48 AM, Willem Ferguson 
>> <willemferguson at zoology.up.ac.za 
>> <mailto:willemferguson at zoology.up.ac.za>> wrote:
>> My formulation, reflecting my strong deficiencies in Qt coding but 
>> following the above, for the new connection is:
>> connect(this, 
>> ui.timeDiffEdit->timeChanged(ui.timeDiffEdit->time()),this, 
>> this->timeDiffEditChanged());
>> The second parameter needs to be a pointer, for which I used 
>> ui.timeDiffEdit. The timeChanged() signal needs a QTime value, so I 
>> provided that with ui.timeDeffEdit->time(), the actual amount of time 
>> by which the timeDiffEdit has been changed.
>> The last parameter also needs an address, provided by 
>> this->timeDiffEditChanged() is the response to the signal 
>> fromtimeDiffEdit->timeChanged(). It is a void function and the source 
>> of build problems. The compiler generates an error:
>> /home/willem/src/subsurface/desktop-widgets/importgps.cpp:30:104: 
>> error: invalid use of void expression
>> connect(this, ui.timeDiffEdit->timeChanged(ui.timeDiffEdit->time()), 
>> this, this->timeDiffEditChanged());
>> ^
>> Obviously, accessing the pointer this->timeDiffEditChanged() should 
>> not return a void value. I have no idea of how to respond to this 
>> error. Any suggestions are very welcome.
> How about
> connect(this, &QTimeEdit::timeChanged, this, 
> &ImportGPS::timeDiffEditChanged);
> That seems like it would follow the syntax suggested above, right?
> /D

Thank you very much for your time.

For Dirk's suggestion I get:

/home/willem/src/subsurface/desktop-widgets/importgps.cpp: In 
constructor ‘ImportGPS::ImportGPS(QWidget*, QString, 
/home/willem/src/subsurface/desktop-widgets/importgps.cpp:30:78: error: 
no matching function for call to ‘ImportGPS::connect(ImportGPS*, void 
(QDateTimeEdit::*)(const QTime&), ImportGPS*, void (ImportGPS::*)())’
   connect(this, &QTimeEdit::timeChanged, this, 

I suspect this means that there is a problem in the types of parameters 
in the call to connect() ??

For Bill's formulation there is an apparent problem with the signal part 
of the call to connect():

/home/willem/src/subsurface/desktop-widgets/importgps.cpp:31:88: error: 
invalid use of non-static member function ‘void 
QDateTimeEdit::timeChanged(const QTime&)’
   connect(ui.timeDiffEdit, ui.timeDiffEdit->timeChanged, this, 
I just do not know how to proceed.

Kind regards,


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