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Thread: why is the sender's type of the destroyed() signal QPushButtonPrivate?

  1. #1
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    Default why is the sender's type of the destroyed() signal QPushButtonPrivate?

    I have a delegate class that inherits from QStyledItemDelegate. In SlotDestroyed(): why is sender() of the type QPushButtonPrivate and not QPushButton?

    Qt Code:
    1. QWidget *Delegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
    2. {
    3. QPushButton *btn = new QPushButton(parent);
    4. btn->setText("test");
    5.  
    6. connect(btn, SIGNAL(destroyed(QObject*)), this, SLOT(SlotDestroyed(QObject*)));
    7. return btn;
    8. }
    9.  
    10.  
    11. void Delegate::SlotDestroyed(QObject* editor)
    12. {
    13. QPushButton *btn = qobject_cast<QPushButton*>(sender()); // why null?
    14. QObject *s = sender();
    15. btn = reinterpret_cast<QPushButton*>(sender());
    16. }
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  2. #2
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    Default Re: why is the sender's type of the destroyed() signal QPushButtonPrivate?

    Probably because QPushButton is implemented in two parts, with an outer "public" class and an inner "private" one. Lots of Qt classes have this two-part implementation, for "security" reasons, to make it easier for object data to be shared, and to make object assignment simpler and lighter-weight.

    However, the behavior you've discovered is probably technically a bug.

  3. #3
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    Default Re: why is the sender's type of the destroyed() signal QPushButtonPrivate?

    Out of interest, how are you going to use a pointer to an object that is advertising its imminent demise?

  4. #4
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    Default Re: why is the sender's type of the destroyed() signal QPushButtonPrivate?

    To release some resources (which I'm doing in the destructor now). I was just wondering if that's a bug or if there is a reason for that behavior.

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