[FIXED] How can I retrieve a signal parameter with New-Style Syntax?

Issue

Inside a custom button class I have a signal which emits when is dropped something into it. Here the relevant method:

class CustomButton

   linked = QtCore.pyqtSignal()
   ...

   def dropEvent(self, e):
        print e.source().objectName()
        print self.objectName()
            # set the drop action as LinkAction
        e.setDropAction(QtCore.Qt.LinkAction)
        # tell the QDrag we accepted it
        e.accept()
        #Emit linked signal with the drag object's name as parameter
        self.linked.emit( e.source().objectName() )
        return QtGui.QPushButton.dropEvent(self, QtGui.QDropEvent(QtCore.QPoint(e.pos().x(), e.pos().y()), e.possibleActions(), e.mimeData(), e.buttons(), e.modifiers()))

In otherhand, outside the class, in the main application I'm creating a slot, and a way to connect it to the signal.

#The slot (actually is just a python callable)
def on_link(self):
    input = self.sender().objectName()[4:]
    print input
    #I need to print the name of the other object emitted as str parameter in the signal....

#Instance of custom button
custom_button.linked.connect( lambda: on_link( custom_button )  )

At this point I already know that I can get the sender() of the signal, however, I don't know how to get the parameter of self.linked.emit( e.source().objectName() ). I just know that first I have to change first this: linked = QtCore.pyqtSignal(str), but don't know how to write the connection or the slot and retrieve the e.source().objectName() in the emit signal.

Solution

The current design of the slot looks very confusing. At first glance, it looks like an instance method, but it is actually just a module-level function with a fake self parameter.

I would suggest something simpler, and more explicit, like this:

class CustomButton(QtGui.QPushButton):
    linked = QtCore.pyqtSignal(str, str)

    def dropEvent(self, event):
        ...
        self.linked.emit(self.objectName(), event.source().objectName())
        return QtGui.QPushButton.dropEvent(self, event)

def on_link(btn_name, src_name):
    print btn_name, src_name

custom_button.linked.connect(on_link)

An alternative design would be to send the objects, instead of their names:

    linked = QtCore.pyqtSignal(object, object)
    ...
    self.linked.emit(self, event.source())

def on_link(button, source):
    print button.objectName(), source.objectName()

Answered By - ekhumoro