Get signal sender

[wombats]

Hi,

I use PureBasic, which uses Qt for its GUI implementation on Linux. While PureBasic provides access to a measure of the Qt API, it doesn't give everything I need, so I'm developing a shared library I can use with my program to make use of more of what it offers.

I connect signals to the PureBasic 'gadgets' like this:

qApp->connect(header, &QHeaderView::sectionClicked, header, &ListIconHeaderClicked)

qApp->connect(header, &QHeaderView::sectionClicked, header, &ListIconHeaderClicked)

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In this example, I am trying to detect when the header of PureBasic's ListIconGadget, which uses QTreeWidget, is clicked.

I'm not sure how I could use classes in this situation, since I know you can use QObject::sender() to get the signal sender. Is there a way I can find out which widget send the signal in the ListIconHeaderClicked(int logicalIndex) function?

Thank you.

[d_stranz]

qApp->connect(header, &QHeaderView::sectionClicked, header, &ListIconHeaderClicked)

This is incorrect syntax for a connect() statement. The first half is OK - you are saying you want to connect to an instance of the QHeaderView class ("header") and its sectionClicked() signal. The second half is wrong for two reasons: first, if you want to handle that signal in some other class that you have implemented, then you put the instance pointer for that class as the third argument (not "header"); and second, the next argument must be the address of a method for the class you used as the third argument:

connect( header, &QHeaderView::sectionClicked, myClass, &MyClass::onSectionClicked ); // or whatever you call your class and slot

connect( header, &QHeaderView::sectionClicked, myClass, &MyClass::onSectionClicked ); // or whatever you call your class and slot

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Calling connect() through a qApp pointer is not necessary unless you are doing it from some code that is not in a class derived from QObject. QObject implements the connect() methods and all derived classes inherit them. Your slot definition should look like this:

class MyClass : public SomeClassDerivedFromQObject
{
   Q_OBJECT
 
// constructor, destructor, etc.
 
public slots:
    void onSectionClicked( int logicalIndex );
};
 
void MyClass::onSectionClicked( int logicalIndex )
{
 
  // do whatever you want with the header and index.
  // If you need the pointer to the QHeaderView:
 
  QHeaderView * pView = qobject_cast< QHeaderView * >( sender() );
  if ( pView != nullptr )
  {
      // Safe to use the pView pointer
  }
}

class MyClass : public SomeClassDerivedFromQObject
{
   Q_OBJECT

// constructor, destructor, etc.

public slots:
    void onSectionClicked( int logicalIndex );
};

void MyClass::onSectionClicked( int logicalIndex )
{

  // do whatever you want with the header and index.
  // If you need the pointer to the QHeaderView:

  QHeaderView * pView = qobject_cast< QHeaderView * >( sender() );
  if ( pView != nullptr )
  {
      // Safe to use the pView pointer
  }
}

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