Using pyqtSignal in emitting signal for maptool in QGIS

Question

For QGIS I have a plugin named GGAImporter:

from .point_tool import PointTool
class GGAImporter:
...
    def addFachdatum(self):
        self.mapTool = PointTool(self.iface.mapCanvas())
        self.beforeMapTool=self.iface.mapCanvas().mapTool()
        self.iface.mapCanvas().setMapTool(self.mapTool)
        self.mapTool.canvasClicked.connect(self.onMapClick)
    
    def onMapClick(point):
        logging.warning('onMapClick: '+point.asWkt())

In a several file point_tool.py there is the class for the tool:

from qgis.gui import QgsMapTool, QgsMapToolEmitPoint
from qgis.core import Qgis, QgsMessageLog
from PyQt5.QtCore import pyqtSignal

class PointTool(QgsMapToolEmitPoint): 
    canvasClicked = pyqtSignal('QgsPointXY')
    
    def __init__(self, canvas):
        super(QgsMapTool, self).__init__(canvas)

    def canvasReleaseEvent(self, event):
        point_canvas_crs = event.mapPoint()

        self.canvasClicked.emit(point_canvas_crs)
        QgsMessageLog.logMessage('canvasReleaseEvent '+point_canvas_crs.asWkt()) 

The logmessage from point_tool is correctly:

2021-11-19T09:51:29     WARNING    canvasReleaseEvent POINT(646484.461160849314183 5857199.37299698870629072)

But in GGAImporter-class I get an error:

2021-11-19T09:51:29     WARNING    Traceback (most recent call last):
              File "C:/Users/sschmidt/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\gga_importer\gga_importer.py", line 427, in onMapClick
              logging.warning('onMapClick: '+point.asWkt())
             AttributeError: 'GGAImporter' object has no attribute 'asWkt'

It seems that the parameter of type QgsPointXY by emitting to slot get lost and is then my main-class of the plugin. Is there an error with PyQt5.QtCore.pyqtSignal?

Answer 1

You just forgot to add self as the first argument of your onMapClick() method. The class instance object needs to be the first argument of all class methods. The canvasClicked() signal also emits the Qt.MouseButton object which caused the event which you can also catch.

Your slot method definition should look like:

def onMapClick(self, point, button):
    logging.warning('onMapClick: '+point.asWkt())