Connect PySide to a signal using QSignalMapper and an instance method

Question

I have a small app with a table. This table has some data and a button on each row. These buttons should allow the user to remove corresponding row data. I'm trying to implement it via the clicked button signal, but I need to pass the row number, so I tried using QSignalMapper, as shown in the excerpt below

btnRemoveItem = QPushButton()
btnRemoveItem.clicked.connect(self.removeItem)
self.mapper = QSignalMapper(self)
self.connect(btnRemoveItem, QtCore.SIGNAL("clicked()"), self.mapper,
        QtCore.SLOT("map()"))
self.mapper.setMapping(btnRemoveItem, nextRow)
self.connect(self.mapper, QtCore.SIGNAL("mapped(int)"), self.removeItem(),
        QtCore.SIGNAL("clicked(int)"))

Problem is, my removeItem(self, index) method is an instance method (because my table belongs to a specific class) and I'm having trouble mapping it in a way I can pass self along with index.

Currently, my code fails with the following error:

TypeError: removeItem() takes exactly 2 arguments (1 given)

Is there a way to make this work correctly? Or is it impossible to map instance methods with QSignalMapper in PySide?

Answer 1

I tried to reproduce your code in PyQt but I'm not fully aware of the differences between Pyside and PyQt so my answer is more of a guess. Try to remove the second line of your code and replace the last one with:

self.mapper.mapped.connect(self.removeItem)

Answer 2

In the last line of your code, in the connect method, I believe you have a typo in your code

self.connect(self.mapper, QtCore.SIGNAL("mapped(int)"), self.removeItem(), 
    QtCore.SIGNAL("clicked(int)"))

should be

self.connect(self.mapper, QtCore.SIGNAL("mapped(int)"), self.removeItem,
    QtCore.SIGNAL("clicked(int)"))

Having self.removeItem() in the connect method will actually try to call the self.removeItem method rather than providing the subsystem an address to connect the function

As finmor suggests, you should look at new syntax signals and slots as they will dramatically help to clarify your code and make it more Pythonic.