How does qtrio._qt.connection() handle signals and slots getting destroyed

[altendky]

Raised at: innodatalabs/triq#5 (comment)

Even if it ought to 'just work out' there should probably be tests added. Though maybe @nicoddemus can elaborate on a scenario where we retain a reference to a signal or slot and they 'go away'. Or perhaps that's the issue and we shouldn't be retaining strong references at all and need to switch to weakrefs.

[nicoddemus]

Here's a quick example demonstrating how connections are automatically undone if one of the sides is destroyed:

from PyQt5.QtWidgets import QApplication, QPushButton


class MyObject:

    def __init__(self, clicks):
        self.clicks = clicks

    def on_click(self):
        self.clicks.append(1)


def main():
    app = QApplication([])

    clicks = []
    obj = MyObject(clicks)

    button = QPushButton()
    button.clicked.connect(obj.on_click)

    button.clicked.emit()
    assert clicks == [1], obj.clicks

    del obj
    # clicking on the button again won't append to the list because the connection
    # is undone automatically
    button.clicked.emit()
    assert clicks == [1], obj.clicks


main()