QStyledItemDelegate Weird Error

[daleotar]

Hi.

I'm subclassing a QStyledItemDelegate in order to attach it to a QTableWidget.
It is working fine but I want to emit a signal from the delegate when I do some stuff inside the call of reimplemented QStyledItemDelegate::setEditorData, for instance:

class MyDelegate : public QStyledItemDelegate
{
    Q_OBJECT
 
public:
    MyDelegate(QObject* parent);
    QWidget *createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const;
    virtual void setEditorData(QWidget *editor, const QModelIndex &index) const;
    virtual void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const;
    virtual void updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const;
 
signals:
    void mySignal(int value);
 
};
 
void MyDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
    int i = 1;
    ...do some stuff...
 
    emit mySignal(i);
}

class MyDelegate : public QStyledItemDelegate
{
    Q_OBJECT

public:
    MyDelegate(QObject* parent);
    QWidget *createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const;
    virtual void setEditorData(QWidget *editor, const QModelIndex &index) const;
    virtual void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const;
    virtual void updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const;

signals:
    void mySignal(int value);

};

void MyDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
    int i = 1;
    ...do some stuff...

    emit mySignal(i);
}

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However I have a problem that I can't understand... The compiler is telling me:
"error: passing 'const MyDelegate' as 'this' argument of 'void MyDelegate::mySignal(int)' discards qualifiers"

I can't understand this error if I'm passing an int as an argument, not a "MyDelegate"...
If someone can explain or knows something about this or maybe, if anyone thinks that this is a bug...
Well, any help is appreciated...

[Santosh Reddy]

Define the signal this way,

...
signals:
    void mySignal(int value) const;
...

...
signals:
    void mySignal(int value) const;
...

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[daleotar]

Thanks Santosh for your very opportune reply like always...

Well, Now it works, thanks a lot... However now my question is why do we have to define the signal as a const?

Again...Thanks a lot, XD

[Santosh Reddy]

a const function can call only another const function(s), signal is also a function, but you don't need to implement it, Qt (moc) will implement it for you.

[daleotar]

thanks for the clarification, I'm feeling like an idiot because the solution is kinda obvious, XD