compile issue, syntax i guess, but can't find it

[incapacitant]

archiv.h

class Archives : public QDialog
{
    Q_OBJECT
 
public:
  Archives( QWidget *parent = 0 );
  ~Archives();
  QString getFileName( const QModelIndex &);
...

class Archives : public QDialog
{
    Q_OBJECT

public:
  Archives( QWidget *parent = 0 );
  ~Archives();
  QString getFileName( const QModelIndex &);
...

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archiv.cpp

//****************************************************************
QString Archives::getFileName( const QModelIndex & idx )
{
  return model->data(idx.sibling(idx.row(), 0)).toString();
}

//****************************************************************
QString Archives::getFileName( const QModelIndex & idx )
{
  return model->data(idx.sibling(idx.row(), 0)).toString();
}

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and menu.cpp

//****************************************************************
void ApplicationWindow::archives()
{
  Archives Archives_dlg( this );
  if ( Archives_dlg.exec() )
  {
     QString s = Archives_dlg->getFileName( const QmodelIndex & idx);
  }  
}

//****************************************************************
void ApplicationWindow::archives()
{
  Archives Archives_dlg( this );
  if ( Archives_dlg.exec() )
  {
     QString s = Archives_dlg->getFileName( const QmodelIndex & idx);
  }  
}

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and the compiler says :
QString s = Archives_dlg->getFileName( const QmodelIndex & idx);
180 C:\Qt\test\sms\menu.cpp base operand of `->' has non-pointer type `Archives'

in the procedure above I make a similar call with (apparently the same syntax) and it works, so I don't know.