Getting coordinates from mouse click in QGIS3 in a plugin

Question

I'm trying to grab the coordinates from a click. If I type this code (obtained from Getting coordinates from mouse click in QGIS 3 (python plugin)):

def display_point(pointTool):
    try:
        print(pointTool.x(), pointTool.y())
    except AttributeError:
        pass

# a reference to our map canvas
canvas = iface.mapCanvas()
# this QGIS tool emits as QgsPoint after each click on the map canvas
pointTool = QgsMapToolEmitPoint(canvas)
pointTool.canvasClicked.connect(display_point)
canvas.setMapTool(pointTool)
display_point(pointTool)

in the python console it works perfectly. But if I place it inside my plugin class it does not work, don't even get the cross mouse pointer and I have no idea why is not working:

...
    def display_point(self, pt, bt):
        try:
            print(pt.x(), pt.y(), bt)
        except AttributeError:
            print("No attribute")

    def on_create_ignition_point(self):
        print("IN")
        canvas = self.iface.mapCanvas()
        pointTool = QgsMapToolEmitPoint(canvas)
        pointTool.canvasClicked.connect(self.display_point)
        canvas.setMapTool(pointTool)
        print('OUT')
...

the function on_create_ignition_point gets called from a toolbar button and the IN and OUT messages are printed. Also created a class like is explained in Getting coordinates of point on mouse click using PyQGIS with the same results.

Any hints on what I'm doing wrong?

Answer 1

Following the comments provided did the trick. Moving the local variables to instance attributes solved the problem.

The final code is this:

        if not (self._pointTool is None):
            self._pointTool.canvasClicked.disconnect()
            del self._pointTool
            self._previousTool = None
            self._pointTool = None
        # Store the previous tool in use b the user
        canvas = self._iface.mapCanvas()
        self._previousTool = canvas.mapTool()
        # Set the tool and onClick callback
        self._pointTool = QgsMapToolEmitPoint(canvas)
        self._pointTool.canvasClicked.connect(self.on_point_callback)
        canvas.setMapTool(self._pointTool)