autodelete pointer QList

firen

Hi,

in old QT3 we had QPtrList which was able to delete automatically (method: setAutoDelete) objects after the pointer was removed from list (https://linux.die.net/man/3/qptrlist). What would a good option to get this done with a QList (from Qt5/6)?
Should I override QList or could I get this done more directly?

Thank you!

SGaist

Hi,

Check qDeleteAll.

ChrisW67

@SGaist is on the money if you want to delete everything in the list.

If you want only single items to be deleted when removed from a list of bare pointers then

QList<T*> list;
...
delete list.takeAt(1);

is about as simple as it gets.

To avoid direct delete smart pointers might work for you:

#include <QCoreApplication>
#include <QList>
#include <QDebug>

#include <memory>

class Blah {
public:
    Blah(int i): m_num(i) { qDebug() << m_num << "Blah()" << this; }
    ~Blah()               { qDebug() << m_num << "~Blah()" << this; }
private:
    int m_num;
};

int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);
    QList<std::shared_ptr<Blah> > list;
    list.append(std::make_shared<Blah>(0));
    list.append(std::make_shared<Blah>(1));
    list.append(std::make_shared<Blah>(2));
    list.append(std::make_shared<Blah>(3));
    qDebug() << "Before remove";
    list.removeAt(1);
    qDebug() << "After remove";
    return 0;
}

0 Blah() 0x5584039f4c60
1 Blah() 0x5584039f57a0
2 Blah() 0x5584039f51c0
3 Blah() 0x5584039f5ae0
Before remove
1 ~Blah() 0x5584039f57a0
After remove
3 ~Blah() 0x5584039f5ae0
2 ~Blah() 0x5584039f51c0
0 ~Blah() 0x5584039f4c60

firen

@ChrisW67 Thank you! Yes, I thought about smart pointers as well but I am (yet) not very familiar with it and don't know which one is correct. Currently we work most of the time with raw pointers and the old Qt3 QPtrList .

Maybe the qt-version: https://forum.qt.io/topic/19073/any-difference-between-std-shared_ptr-and-qsharedpointer/2 could be an option as well...