Exception when reading widget store on QVector

n34rt

Why when i write like the first example i get an exception in the layout->addWidget line
and when i write like the second example i get no exception?

//1
class SpinnerButton : public QPushButton
{
    Q_OBJECT

public:

    QLabel* lbl;
    QLabel* lbl2;
    QVector<QLabel*> lbl_vec { lbl, lbl2 };
    //...
}

for (int i = 0; i < 2; i++)
{
    lbl_vec[i] = new QLabel(this);
    //...
}

QGridLayout* layout = new QGridLayout();
this->setLayout(layout);
layout->addWidget(lbl, 0, 1, Qt::AlignRight); // <- exception

//2
class SpinnerButton : public QPushButton
{
    Q_OBJECT

public:

    QLabel* lbl = new QLabel(this);
    QLabel* lbl2 = new QLabel(this);
    QVector<QLabel*> lbl_vec { lbl, lbl2};
    //...
}

for (int i = 0; i < 2; i++)
{
    lbl_vec[i]->setText("Loading");
    //...
}

QGridLayout* layout = new QGridLayout();
this->setLayout(layout);
layout->addWidget(lbl, 0, 1, Qt::AlignRight); // <- no exception

Also, is it wrong to initialize a label in a subclass header like this?

public:
    QLabel* lbl = new QLabel(this);

jsulm

@n34rt said in Exception when reading widget store on QVector:

QVector<QLabel*> lbl_vec { lbl, lbl2 };

At that time lb1 and lb2 are invalid pointers! So, if you use them your app will crash.

JonB

@n34rt said in Exception when reading widget store on QVector:

layout->addWidget(lbl, 0, 1, Qt::AlignRight); // <- exception

layout->addWidget(lbl, 0, 1, Qt::AlignRight); // <- no exception

Did you run your code in a debugger to answer this? In the first case (QLabel* lbl;) lbl is an uninitialized variable so it "crashes", in the second case (QLabel* lbl = new QLabel(this);) lbl is set to a QLabel so it does not. Don't know what else you would expect. There is no relevance to the QVector you mention in your title or your lbl_vec.

QLabel* lbl = new QLabel(this);

You can put that in a class declaration/header if you wish. Personally I would not: I would do the lbl = new QLabel(this); in the class's constructor code.

jsulm

@n34rt said in Exception when reading widget store on QVector:

QVector<QLabel*> lbl_vec { lbl, lbl2 };

At that time lb1 and lb2 are invalid pointers! So, if you use them your app will crash.