failed connect

[nischu]

Hello there, I'm trying from a tutorial making a small tictactoe game with Qtcreator. That's my first project with Qt.
When I run the binary, I get these two messages:

Starting /home/sven/develop/Qt/build-tictactoe-Desktop_Qt_5_6_0_GCC_64bit-Debug/tictactoe...
QObject::connect: No such signal TicTacToeWidget::currentPlayerChanged(TicTacToeWidget::Player) in ../tictactoe/mainwindow.cpp:17
QObject::connect:  (sender name:   'gameBoard')
QObject::connect:  (receiver name: 'MainWindow')
QObject::connect: No such signal TicTacToeWidget::gameOver(TicTacToeWidget::Player) in ../tictactoe/mainwindow.cpp:20
QObject::connect:  (sender name:   'gameBoard')
QObject::connect:  (receiver name: 'MainWindow')

But i have both functions in the 'signals' part in the class declaration of TicTacToeWidget.
What else could be caused this errors?

[mrjj]

hi and welcome
One common error is that moc.exe was not run so it dont know it has the signals.
Or forgetting the Q_OBJECT macro in the class .h

So check if u have Q_OBJECT
do clean all
run qmake
rebuild

if it still says it, please post some code :)

[nischu]

Q_OBJECT is set, and the build process was without warnings.

The perfidious is, that i have all source files belonging to the tutorial so i was being able to compare these to my own try. But although I compared every piece of code, I didn't found a semantic distinction.
Only the *.ui files I couldn't check, that would too wearisome for me.

Here the code for the connect statements:

MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    connect( ui->actionNewGame, SIGNAL(triggered()),
             this, SLOT(startNewGame()));

    connect( ui->actionQuit, SIGNAL(triggered()),
             qApp, SLOT(quit()));

    connect( ui->gameBoard, SIGNAL(currentPlayerChanged(TicTacToeWidget::Player))
             , this, SLOT(updateNameLabels()));

    connect( ui->gameBoard, SIGNAL(gameOver(TicTacToeWidget::Player))
             , this, SLOT(handleGameOver(TicTacToeWidget::Player)));
}

The first two connections will created fine.

I suppose i made a mistake within Designer Mode, but i have no clue where.
Could it be that I made a mistake at naming the sender's source? But i don't see such thing, in the Designer Mode's Object Inspector.

[mrjj]

@nischu said:
hi the UI is just translated into code. ( the setUI function)
so i doubt it has anything to do with it.

also since you use directly connect, you are in control.

one thing i do wonder

connect( ui->gameBoard, SIGNAL(currentPlayerChanged(TicTacToeWidget::Player))
, this, SLOT(updateNameLabels()));

should that not be
connect( ui->gameBoard, SIGNAL(currentPlayerChanged(TicTacToeWidget::Player))
, this, SLOT(updateNameLabels(TicTacToeWidget::Player)));

anyway, you can check what connect returns to see if it fails

qDebug() << "con1:" << connect(xxx

it says TRUE when it accepts the connect.

[nischu]

@mrjj said:
should that not be
connect( ui->gameBoard, SIGNAL(currentPlayerChanged(TicTacToeWidget::Player))
, this, SLOT(updateNameLabels(TicTacToeWidget::Player)));

No, it's ok. Here the handling:

void MainWindow::updateNameLabels()
{
    QFont f = ui->player1->font();
    f.setBold( ui->gameBoard->currentPlayer() == TicTacToeWidget::Player1);
    ui->player1->setFont(f);
    f.setBold( ui->gameBoard->currentPlayer() == TicTacToeWidget::Player2);
    ui->player2->setFont(f);
}

Thanks for your hint with QDebug. But that says no news: con1,con2 == true, con3,con4 == false

[mrjj]

Hi if you can zip the whole project, i could have a look?
or link to the tut.
or show the .h and .cpp where signals/slots are defined

[nischu]

mrjj, Thanks for taking your time looking over my source code.
[Here are my own files]

[And here the files published by my book] This compiles and runs without errors.

[jerome_isAviable]

Hi @nischu,
when you connect signal and slot the sign has to be exactly the same.
If you have a signal signed: currentPlayerChanged(TicTacToeWidget::Player)
you need to link with a slot signed: compatibleSlotToBeLinked(TicTacToeWidget::Player)

if not, the link not occur as specified in the doc (just before "Advanced Signals and Slots Usage" not far from the end of the article doc.

http://doc.qt.io/qt-5/signalsandslots.html

[mrjj]

@nischu

hi as @jerome_isAviable says

it was the name space/scope naming that confused it.
"player" vs "TicTacToeWidget::player"

void currentPlayerChanged( Player);
works if
void currentPlayerChanged( TicTacToeWidget::Player );

here is fixed and running sample
https://www.dropbox.com/s/jvsoulsvmh3292g/tictactoe.zip?dl=0

[VRonin]

Despite almost all the documentation still using SIGNAL() and SLOT(), you should really switch to the Qt5 syntax https://wiki.qt.io/New_Signal_Slot_Syntax it catches these problems at compile time and makes it easier to solve them

[mrjj]

@VRonin
I complete agree that the new syntax has much better checks etc
but sadly its very unfriendly to
beginners when overloaded signals are used.

connect(spinbox, static_cast<void (QSpinBox::*)(int)>(&QSpinBox::valueChanged), slider, &QSlider::setValue);
vs
connect(spinbox, SIGNAL(valueChanged(int)), slider, SLOT(setValue(int)));

Its sad that compile time check has such a high price in syntax complexity and
pretty ugly to look at :) ( IMO)

update:
just seen that Qt 5.7 has qOverload
so my point is not so valid :)

[nischu]

Thank you all for helping detect ths error. I will take a close look at the related docs.
Regards, Nico