Checking which item is on focus with QGraphicsItem.focusItem()

Question

So here's this exercise I'm doing, where I need to create squares in a QGraphicsScene whenever I click "create_button" and when I click on any of the squares the name of that square should be displayed in a QLabel, which is under the QGraphicsView, and here's how I'm trying to do that.

This is the window that I use

and here's the code

    
class rectangles(QtWidgets.QDialog):

    def __init__(self):
        super(rectangles, self).__init__()
        
        loader = QtUiTools.QUiLoader()
        self.ui = loader.load(ui_path, self)
        self.variables()
        
        self.ui.create_button.clicked.connect(self.creator)
        self.scene.focusItemChanged.connect(self.nameDisplay)
        
    def variables(self):        
        self.scene = QtWidgets.QGraphicsScene()
        self.ui.canvas_area.setScene(self.scene)
        self.current_focus_obj = QGraphicsItem.focusItem() #the problem is in here
         
    def creator(self): 
        rect = self.scene.addRect(-20,-20,40,40, QPen(Qt.red), QBrush(Qt.gray))
        rect.setFlag(QGraphicsItem.ItemIsMovable)
        rect.setFlag(QGraphicsItem.ItemIsFocusable)
        rect.setFlag(QGraphicsItem.ItemIsSelectable)
        num_list.remove(num_list[0])
        
    def nameDisplay(self):
        self.ui.name_line.setText(str(self.current_focus_obj)) #Here I try to set 
                                                               #the name of the 
                                                               #active rectangle 
                                                               #to my QLabel      
                
if __name__ == '__main__':
    rectangles_window = rectangles()
    rectangles_window.ui.show()

However, when I run this code I get the following error:

# Error: TypeError: file <maya console> line 32: descriptor 'focusItem' of 'PySide2.QtWidgets.QGraphicsItem' object needs an argument # 

To be honest, I don't really understand what argument I should pass in focusItem() and that's what the problem is. I thought it didn't need any arguments as it should return any abject that is currently on focus. This might be a small problem but it's really slowing down my pace right now, so if someone could help I would really appreciate that:)

Answer 1

You aren't respecting the signal QGraphicsScene::focusItemChanged. You have to connect it to a function that receives those parameters:

def nameDisplay(self, newFocusItem, oldFocusItem, reason):
    # ...presumably use newFocusItem

It is also wrong to write:

self.current_focus_obj = QGraphicsItem.focusItem()

because that function is not static. It must be called on an instance of QGraphicsItem.