Direct connect a built-in signal from one class to a slot on another class

Habibie

@JonB said in Direct connect a built-in signal from one class to a slot on another class:

@Habibie
You say this works:
connect(ui->comboBox, SIGNAL(currentIndexChanged(int)), this, SIGNAL(indexChanged(int)));
and it's inside DialogOne::DialogOne().

The above uses the old string SIGNAL/SIGNAL connection style.

Then you say you changed to
connect(comboBox, QOverload<int>::of(&QComboBox::currentIndexChanged), [=](int index){
still inside DialogOne::DialogOne().

The compiler says

../src/dialogone.cpp:12:13: error: ‘comboBox’ was not declared in this scope

Why have you changed from ui->comboBox to comboBox?

The above uses a new functional connection with lambda.

BTW, with an old style string SIGNAL/SIGNAL connection, if I change from this

    connect(ui->comboBox, SIGNAL(currentIndexChanged(int)), this, SIGNAL(indexChanged(int)));

to this

    connect(comboBox, SIGNAL(currentIndexChanged(int)), this, SIGNAL(indexChanged(int)));

the compilation spits out the following error messages.

g++ -c -pipe -g -std=gnu++11 -Wall -Wextra -D_REENTRANT -fPIC -DGIT_VERSION=\"\" -DGIT_HASH=\"febc5d8c3a77a4a9039601f638b0ce220c3b3189\" -DQT_QML_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../../SignalsAndSlots-01 -I. -I../include -I/usr/include/x86_64-linux-gnu/qt5 -I/usr/include/x86_64-linux-gnu/qt5/QtWidgets -I/usr/include/x86_64-linux-gnu/qt5/QtGui -I/usr/include/x86_64-linux-gnu/qt5/QtCore -I. -I. -I/usr/lib/x86_64-linux-gnu/qt5/mkspecs/linux-g++ -o dialogone.o ../src/dialogone.cpp
../src/dialogone.cpp: In constructor ‘DialogOne::DialogOne(QWidget*)’:
../src/dialogone.cpp:12:13: error: ‘comboBox’ was not declared in this scope; did you mean ‘QComboBox’?
   12 |     connect(comboBox, SIGNAL(currentIndexChanged(int)), this, SIGNAL(indexChanged(int)));
      |             ^~~~~~~~
      |             QComboBox
make: *** [Makefile:566: dialogone.o] Error 1

SGaist

Hi,

That's exactly the point of @JonB, there's no reason to remove the ui-> from your code.

Habibie

@SGaist said in Direct connect a built-in signal from one class to a slot on another class:

Hi,

That's exactly the point of @JonB, there's no reason to remove the ui-> from your code.

Got it and thank you for pointing it out.