Link a ui.log with a logger handler and move this UI look like create the mem leak

[mathisschmidt]

First Check

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Example Code

import logging
from dataclasses import dataclass

from nicegui import ui
from datetime import datetime
import pandas as pd
import io

from nicegui.elements.aggrid import AgGrid
from nicegui.elements.log import Log

from idfc_parser.parser import IdfcTransactionsParser
from idfc_parser.payment import Payment
from nicegui.events import UploadEventArguments

@dataclass
class Filter:
    year: int
    month: int

class LogElementHandler(logging.Handler):
    """A logging handler that emits messages to a log element."""

    def __init__(self, element: ui.log, level: int = logging.NOTSET) -> None:
        self.element = element
        super().__init__(level)

    def emit(self, record: logging.LogRecord) -> None:
        try:
            msg = self.format(record)
            self.element.push(msg)
        except Exception:
            self.handleError(record)

class IndexGUI:
    def __init__(self):
        self.log_container: Log = ui.log(max_lines=10).classes('w-full h-96 overflow-y-auto bg-gray-900 p-4 rounded hidden')

    def create_ui(self):
        # Setup logger to use LogElementHandler
        logger = logging.getLogger('idfc_parser.parser')
        handler = LogElementHandler(self.log_container)
        logger.addHandler(handler)
        ui.context.client.on_disconnect(lambda: logger.removeHandler(handler))

        # Header
        self.header()

    def header(self):
        # Main UI
        with ui.header().classes('bg-slate-900 shadow-lg'):
            with ui.row().classes('w-full items-center justify-between px-4'):
                # Right section
                ui.button(
                    'Logs',
                    on_click=self.logs_dialog,
                    icon='description'
                ).classes('bg-purple-600 hover:bg-purple-700')

    def logs_dialog(self):
        """Show logs dialog"""
        with ui.dialog() as dialog, ui.card().classes('w-[600px]') as log:
            ui.label('Parser log').classes('text-xl font-bold mb-4')
            self.log_container.move(log)
            self.log_container.classes(remove='hidden')
            ui.button('Close', on_click=dialog.close).classes('mt-4')

        dialog.open()

Description

My question is why I still have the issue with "Client has been deleted but is still being used. This is most likely a bug in your application code. See #3028 for more information.". I read the issue in the link but I don't see what I am doing wrong.

Is it because I move it? But even when I didn't open the dialog before it is showing this. Please if you have idea share with me I am clueless.

NiceGUI Version

3.5.0

Python Version

3.13.(

Browser

Firefox

Operating System

Linux

Additional Context

No response

[falkoschindler]

Hi @mathisschmidt,

Without being able to run your code, debugging is pretty difficult and inefficient. Can you, please, try to create a minimum reproducible code example by

• removing unused imports and classes,
• removing unnecessary layout and styling,
• making sure to actually create some UI,
• making sure to include ui.run.

Thanks!