[Question] The TextField control fails to render under certain circumstances.

[cccovs]

Question

I need to set the value to None under certain circumstances for subsequent judgment, but it seems that only the background data gets updated while the foreground fails to render the change.

Code sample

from dataclasses import dataclass, field

import flet as ft


@dataclass
@ft.observable
class MainState:
    text: str = field(default='The text currently displayed', init=False)

    def handler_change_text(self, e: ft.Event[ft.Button]):
        self.text = None

@ft.component
def startup():
    state, _ = ft.use_state(MainState())

    return ft.Column(
        controls=[
            ft.TextField(
                value=state.text
            ),

            ft.Button(
                content='change',
                on_click=state.handler_change_text
            )
        ],
        horizontal_alignment=ft.CrossAxisAlignment.CENTER
    )
    

def main(page: ft.Page):
    page.window.width, page.window.height = 300, 200
    page.window.alignment = ft.Alignment.CENTER
    page.render(startup)


if __name__ == '__main__':
    ft.run(main)

Error message

No response

------------------------------------------------------

• I have searched for answers to my question both in the issues and in previous discussions.

[Bbalduzz]

Quick fix, set self.text = "" or add self.notify() after setting to None:

def handler_change_text(self, e):
    self.text = None
    self.notify()

This forces the re-render. Looking at the observable source code, _notify() should be triggered automatically since value_equal(old_string, None) (source) returns False, but something's not working as expected.
Might be worth opening an issue with this repro case: it's a minimal example and the behavior is clearly a bug.

[Bbalduzz]

#5979 (comment)