How to check object is valid.

  • Hello.
    I have my class object, if i have this object on the different places and when i deleted and initialized this object to NULL i want this object would be NULL on all the other places. It is possible?

    #include "mainwindow.h"
    #include <QApplication>
    #include "QDebug"
    class A {
            int x;
            int y;
    class B : public A {
            B(int a, int b) {
                this->m = a;
                this->n = b;
            int m;
            int n;
    int main(int argc, char *argv[])
        QApplication a(argc, argv);
        B* temp = new B(1, 2);
        B* b1 = temp;
        B* b2 = temp;
        delete temp;
        temp = NULL;
        qDebug() << b1->x << b2->x; //its print 421312312 -2131231231
        return a.exec();

  • am using QSharedPointer.
            QSharedPointer<B> obj = QSharedPointer<B>(new B(1, 2));
            B* t =;
            if (t)
                qDebug() << t->m << t->n;
            else {
                qDebug() << "NULL";

  • Qt Champions 2018

    @Taz742 said in How to check object is valid.:

    qDebug() << b1->x << b2->x; //its print 421312312 -2131231231

    Yes, it prints garbage because nobody initialises x.

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