外部规则规则的奇异果

Question

I want to specify a special button so I don't have to adjust every button I use, however I want it's event to trigger a function in a different class.

main.py

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.stacklayout import StackLayout
from kivy.properties import ObjectProperty


class FancyButton(Button):
    imp = ObjectProperty(None)


class Important(StackLayout):

    def NoInspiration(self, smile):
        print("Received: {}".format(smile))


class TestApp(App):
    def build(self):
        pass

if __name__ == '__main__':
    TestApp().run()

test.kv (working)

#:kivy 1.9.0

<FancyButton@Button>:
    on_release: self.parent.NoInspiration(':)')


<Important>:
    id: imp

    FancyButton:
        text: "smiley"

BoxLayout:
    Important

Received: :)

test.kv ( not working)

#:kivy 1.9.0

<FancyButton>:
    on_release: self.parent.NoInspiration(':)')


<Important>:
    id: imp

    BoxLayout:
        FancyButton:
            text: "smiley"

BoxLayout:
    Important

In the 2nd test.kv I added 'BoxLayout:' in front of FancyButton and suddenly I get the error:

AttributeError: 'BoxLayout' object has no attribute 'NoInspiration'

Question

• Why does self.parent only refer to the direct parent and not < Important > in the 2nd example?
• How can I have on_release: in < FancyButton > point to the function NoInspiration() while keeping the function in < Important >?

Follow up questions

• Kivy rule inherence with add_widget()
• Kivy outside rule inherence 2

Answer 1

Change the kv to this

<FancyButton>:
    on_release: self.imp.NoInspiration(':)')


<Important>:
    id: imp

    BoxLayout:
        FancyButton:
            text: "smiley"
            imp: root

BoxLayout:
    Important