On 4/22/22 05:00, Sean Murphy wrote:
I've got an existing class that will be used in both Qt and non-Qt/non-UI applications.
One of that functions within that class parses large text files with what is essentially
a while(!file.eof()) loop. I'd like to add functionality to the class that would provide
some sort of parsing status back to anyone using the class - for example "currently
on loop X of N". Essentially I'd like to add the equivalent of a Qt signal.
The problem with using Qt for any length of time is that you forget how
to do things in the real world.
Long before C++ was even a gleam in the eye of commercial compiler developers,
we did this with C via function pointers.
Take a look at NanoGUI, in particular here:
https://github.com/mitsuba-renderer/nanogui/blob/master/src/example4.cpp
line 211 where they set_callback()
After that go look for the Button class source and the set_callback() method.
You need a different signature, something along the lines of
void (*call_back)( const char *msg, long percentCompleteScaled, long
recordsRead, long recordsFound);
while (whatever)
{
do some reading
if (beenAWhile())
{
if (call_back != nullPtr)
{
call_back( "Still chewing", (recordCount/recordsRead)*100, recordsRead,
recordsFound);
}
}
}
You will need to look up the exact syntax.
If you are designing cross architecture classes and libraries, you have to stop
thinking about Qt. It will mess up your design decisions every time. I just
finished a project using NanoGUI. Getting out of the Signals & Slots mindset
was a tough and bitter cookie to chew. The reality is, with today's language
standard you pretty much don't need them unless you need the ability to queue the
execution to a different thread.
I'm not a fan of lambdas because you can return to an object that has been
deleted. Having said that, if you are properly controlling the lifespan of your
object they can be safe.
Oh, just to save you looking it up, here's how they defined set_callback
/// Set the push callback (for any type of button).
void set_callback(const std::function<void()> &callback) { m_callback =
callback; }
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