Signals and Slots

gabor53

Hi,
I have the following code:

    connect(ui->notes_TextEdit, &QTextEdit::textChanged, [&]()
    {
        notes = getNotes ();
    });

Get notes is defined as

  QString getNotes();

in .h.
The function:

QString Additem::getNotes()
{
    notes = ui->notes_TextEdit->toPlainText ();
    notes = notes.simplified ();

    return notes;
}

Whenever the program execution reaches connect.... the program crashes. The same code works with other variables elsewhere. What is wrong with this one?
Thank you.

hskoglund

Hi, I think in the lambda you're refernce capturing your AddItem instance, try changing to value capture:

connect(ui->notes_TextEdit, &QTextEdit::textChanged, [this]()
{
    notes = getNotes ();
});

gabor53

@hskoglund
I tried and I got an error message:
C:\Programming\Projects\Folkfriends_1_0\additem.cpp:342: error: 'notes' is not captured
notes = getNotes ();
^

hskoglund

Ok, try:

connect(ui->notes_TextEdit, &QTextEdit::textChanged, [this,&]()
{
    notes = getNotes ();
});

gabor53

@hskoglund
Thanks but it generated another error message:

C:\Programming\Projects\Folkfriends_1_0\additem.cpp:340: error: expected identifier before ']' token
connect(ui->notes_TextEdit, &QTextEdit::textChanged, this,&
^
C:\Programming\Projects\Folkfriends_1_0\additem.cpp:342: error: 'notes' is not captured
notes = getNotes ();
^
and the code:

    connect(ui->notes_TextEdit, &QTextEdit::textChanged, [this,&]()
    {
        notes = getNotes ();
    });

hskoglund

Sorry it's tricky with the capture list :-) Try again:

connect(ui->notes_TextEdit, &QTextEdit::textChanged, [=,&notes]()
{
    notes = getNotes ();
});

gabor53

@hskoglund
Now we went further:
I received the following error message:

It happens in a file called atomic_base.h (frankly, I have no idea what that is) .
Here is the file:
atomic_base.h.
The error occurs at line 396.

hskoglund

Hi, I think it's complaining that you're reusing the same variable notes in both the lambda and in getNotes(), try change getNodes something like this:

QString Additem::getNotes()
{
    QString notesTemp = ui->notes_TextEdit->toPlainText ();
    notesTemp = notesTemp.simplified ();

    return notesTemp;
}

gabor53

Same error message in atomic_base.h.

hskoglund

Hmm, that notes QString variable, it's not in your Additem class, is it declared in some other class?

gabor53

@hskoglund
It is declared in Additem.

hskoglund

Ok, I think it's colliding with same other variable notes that you have in your Additem class, most likely a function argument, for example in the function that has that connect statement.

Anyway, suggest to refactor it to same other name, not notes, then you also should be able to use [this], something like this:

connect(ui->notes_TextEdit, &QTextEdit::textChanged, [this]()
{
    anythingButNotes = getNotes ();
});

gabor53

This worked (no idea why):

    connect(ui->notes_TextEdit, &QTextEdit::textChanged, [this]()
    {
       QString notes = getNotes ();
    });

notes is already defined in Additem.h....
Thank you for all your help.