How to iterate QList ?

Anonymous_Banned275

I am not too comfortable using "foreach" ...... however, is there something very basic wrong with my code ?

Or am I missing more ?

define foreach Q_FOREACH

    QList<QObject*>  pLIST = this->children();
    QObject item;

//#ifdef BYPASS
    foreach(auto &pLIST, item )
    {
        text = " Iterate .............  ";

        qDebug().noquote() << text;
    }

One of the errors posted

/home/nov25-1/Qt/5.15.2/gcc_64/include/QtCore/qglobal.h:1085: error: no type named 'const_iterator' in 'QObject'
In file included from settingsdialog.cpp:55:
In file included from ./mainwindow_Bluetooth.h:61:
In file included from ../CCC_SOURCE/A_BT_TEST_A/../dialog_connection.h:4:
In file included from /home/nov25-1/Qt/5.15.2/gcc_64/include/QtWidgets/QDialog:1:
In file included from /home/nov25-1/Qt/5.15.2/gcc_64/include/QtWidgets/qdialog.h:43:
In file included from /home/nov25-1/Qt/5.15.2/gcc_64/include/QtWidgets/qtwidgetsglobal.h:43:
In file included from /home/nov25-1/Qt/5.15.2/gcc_64/include/QtGui/qtguiglobal.h:43:
/home/nov25-1/Qt/5.15.2/gcc_64/include/QtCore/qglobal.h:1085:17: error: no type named 'const_iterator' in 'QObject'
    typename T::const_iterator i, e;
    ~~~~~~~~~~~~^~~~~~~~~~~~~~
settingsdialog.cpp:1241:5: note: in instantiation of template class 'QtPrivate::QForeachContainer<QObject>' requested here
    foreach(auto &pLIST, item )
    ^
/home/nov25-1/Qt/5.15.2/gcc_64/include/QtCore/qglobal.h:1126:21: note: expanded from macro 'foreach'
#    define foreach Q_FOREACH
                    ^
/home/nov25-1/Qt/5.15.2/gcc_64/include/QtCore/qglobal.h:1115:25: note: expanded from macro 'Q_FOREACH'
for (auto _container_ = QtPrivate::qMakeForeachContainer(container); \
                        ^

Christian Ehrlicher

foreach(auto &pLIST, item )

item is not a QList

JoeCFD

@AnneRanch said in How to iterate QList ?:

foreach(auto &pLIST, item )
{
    text = " Iterate .............  ";

    qDebug().noquote() << text;
}

    for( auto const list_item : pLIST )
    {
        text = " Iterate .............  ";
        qDebug().noquote() << text;
    }

Anonymous_Banned275

Thank you, I am not sure why I cannot get the parameters in correct order...
Mental block, I guss.

One more question :
how important is to designate the item as "const" ?

JoeCFD

@AnneRanch my own habit. If list_item is not changed in the loop, you can add a const to enforce it. If anything of list_item is changed by accident, the compiler will tell it is wrong. But maybe no big deal in your app. Up to you.

J.Hilk

I would recommend to no longer use Q_FOREACH it is deprecated for a reason! Use the ranged based for loop the c++ standard offers
for (auto &item : container)

less error prone, less conflict with other libraries, faster compile times.