Multiple AutoCompleters for the same LineEdit box

[Core2]

@mrjj

from mainview.cpp

//Needs better commenting.
void MainView::on_btnAnimalSearch_clicked()
{
    AnimalSearch animalsearch;
    animalsearch.setModal(true);
    connect(&animalsearch, SIGNAL(sendData(QString)), this, SLOT(printData(QString)));
    animalsearch.exec();
}

[mrjj]

@Core2
ok. odd. but dialog works and the widgets in the UI are shown so
that part does work?
I mean, there is no issues with
ui->cmbFilter->addItems(animals); ?
That would really crash if dangling pointer.

[Core2]

@mrjj

yeah that part works and has been for some time. now that i introduced multiple Qcompleters and trying to assign a Qcompleter depending on cmbFilter state is when things started failing. As you can see from the example code above I assign a default of TurtleQcompleter, and then in the section of code:

void AnimalSearch::on_cmbFilter_currentIndexChanged()

runs when the animalsearch ui is started, even though I don't change the cmbFilter, and I try for a test to set the Qcompleter to Rabbit Qcompleter from the earlier assignment of TurtleQcompleter.

[mrjj]

Hi
yes it will fire such signal when current item/index is set.
Also when done in code as doc states
http://doc.qt.io/qt-5/qcombobox.html#currentIndexChanged
So that is pretty normal.

[Core2]

@mrjj

Ok good to know. I will remove my line where I assign a default Qcompleter, and allow this section of code to make the first assignment.

Now i just have to figure out after I make the Qcompleters why i can't assign a different Qcompleter from elsewhere in the code.

Thanks again for your time.

[SGaist]

Can you show the backtrace from your crash ?

[Core2]

@SGaist

backtrace? I don't know what that is.

[SGaist]

It's the list of functions called shown by the debugger when the application crashes.

[mrjj]

Hi
What you mean by
"why i can't assign a different Qcompleter from elsewhere in the code" ?
In what why does it not work ?

[Core2]

@SGaist

I think by watching this video by VoidRealms I will be able to gather this info.
https://www.youtube.com/watch?v=B7UsWtyhXh4

[Core2]

@mrjj

I mean that in the animalsearch ui(new Ui::AnimalSearch) I create the Qcompleters from data i collect from sql into a model that i parse to QstringLists, then in a cmbFilter slot I assign the Qcompleter to the lineBy box.

[mrjj]

@Core2
Ok. that should just work.
I tried the Qt completer sample and there seems to be no issues switching completer.

[Core2]

@mrjj

Interesting. I may set up a test project where i set up a basic program to do this one thing with a cmbFilter, and a LineEdit. Until then I think I go the debugger working and am getting good info. I'm about to respond to SGaist.

[mrjj]

@Core2
Ok. good plan. The call stack will show what happened up till the crash.

[Core2]

@Core2

In the issues window: "c:\blahblahblah\qt\qtbase\src\corelib\tools\qscopedpointer.h:140: error: Debugger encountered an exception: Exception at 0x7747379a, code: 0xc0000005: read access violation at: 0x0, flags=0x0 (first chance)

In the Debugger Window: There is 76 Levels, and there is a yellow arrow pointing to the level 11, AnimalSearch::on_cmbFilter_currentIndexChanged.
The file column of that row contains this animalsearch.cpp
The line row contains 300, which is the line just after the line ui->lineBy->setCompleter(RabbitCompleter);

Looking at the top right window after i click on the level 11, I can see what variables are in memory and what the value and types are (Too freaking cool!)

Is the information i listed above the backtrace?

[mrjj]

Hi
I would check the values of all UI widgets (if non null)
and i would also
change so .h says
QCompleter *TurtleCompleter=0;
QCompleter *RabbitCompleter=0;
QCompleter *DogCompleter=0;
QCompleter *CatCompleter=0;

so im sure they are allocated when i reach crash point ( as in not null)

The error code: 0xc0000005: + 0x0, suggests a null pointer.

[Core2]

@mrjj

Thank you both for taking the time to help me through this. Setting the pointers to 0 first fixed the issue!

I have now added code that looks at the index value of cmbFilter and changes the Qcompleter being used on the lineBy box. Good stuff!

Have a good day!