AttributeError when inheriting from DataTable

[iron3oxide]

Question

I am in the process of writing an extension of DataTable that allows setting the table state with an external model (a polars DataFrame). Since the parameters needed for the parent and its own __init__() method are plentiful, I organized them in Config dataclasses.

When I try to run the code sample below, I get an AttributeError, telling me that ModelDataTable has no attribute named 'callbacks'. I tried debugging this, it seems the __init__() method is never even called, neither is _before_build_command() if I add that.

What am I missing/doing wrong?

Code sample

from dataclasses import asdict, dataclass
from typing import Any, Callable, Optional, Union

import flet as ft
import polars
from flet_core.gradients import Gradient
from flet_core.types import (
    AnimationValue,
    BorderRadiusValue,
    OffsetValue,
    ResponsiveNumber,
    RotateValue,
    ScaleValue,
)


@dataclass
class DataTableConfig:
    ref: Optional[ft.Ref] = None
    width: ft.OptionalNumber = None
    height: ft.OptionalNumber = None
    left: ft.OptionalNumber = None
    top: ft.OptionalNumber = None
    right: ft.OptionalNumber = None
    bottom: ft.OptionalNumber = None
    expand: Union[None, bool, int] = None
    col: Optional[ResponsiveNumber] = None
    opacity: ft.OptionalNumber = None
    rotate: RotateValue = None
    scale: ScaleValue = None
    offset: OffsetValue = None
    aspect_ratio: ft.OptionalNumber = None
    animate_opacity: AnimationValue = None
    animate_size: AnimationValue = None
    animate_position: AnimationValue = None
    animate_rotation: AnimationValue = None
    animate_scale: AnimationValue = None
    animate_offset: AnimationValue = None
    on_animation_end = None
    tooltip: Optional[str] = None
    visible: Optional[bool] = None
    disabled: Optional[bool] = None
    data: Any = None
    border: Optional[ft.Border] = None
    border_radius: BorderRadiusValue = None
    horizontal_lines: Optional[ft.BorderSide] = None
    vertical_lines: Optional[ft.BorderSide] = None
    checkbox_horizontal_margin: ft.OptionalNumber = None
    column_spacing: ft.OptionalNumber = None
    data_row_color: Union[None, str, dict[ft.MaterialState, str]] = None
    data_row_height: ft.OptionalNumber = None
    data_text_style: Optional[ft.TextStyle] = None
    bgcolor: Optional[str] = None
    gradient: Optional[Gradient] = None
    divider_thickness: ft.OptionalNumber = None
    heading_row_color: Union[None, str, dict[ft.MaterialState, str]] = None
    heading_row_height: ft.OptionalNumber = None
    heading_text_style: Optional[ft.TextStyle] = None
    horizontal_margin: ft.OptionalNumber = None
    show_bottom_border: Optional[bool] = None
    show_checkbox_column: Optional[bool] = None
    sort_ascending: Optional[bool] = None
    sort_column_index: Optional[int] = None
    on_select_all = None


@dataclass
class TableCallbackConfig:
    # row callbacks
    on_select_changed_row: Callable | None = None
    on_long_press_row: Callable | None = None
    # cell callbacks
    on_long_press_cell: Callable | None = None
    on_tap_cell: Callable | None = None
    on_double_tap_cell: Callable | None = None
    on_tap_cancel_cell: Callable | None = None
    on_tap_down_cell: Callable | None = None
    # column callbacks
    on_sort_column: Callable | None = None


class ModelDataTable(ft.DataTable):
    def __init__(
        self,
        *,
        model: polars.DataFrame,
        table_config: DataTableConfig = DataTableConfig(),
        call_back_config: TableCallbackConfig = TableCallbackConfig(),
    ) -> None:
        self.model = model
        self.callbacks = call_back_config
        super().__init__(**asdict(table_config))

    @property
    def model(self) -> polars.DataFrame:
        return self._model

    @model.setter
    def model(self, model: polars.DataFrame) -> None:
        self._model = model
        self._render_model()

    def _render_model(self) -> None:
        self.columns = [
            ft.DataColumn(ft.Text(column), on_sort=self.callbacks.on_sort_column)
            for column in self._model.columns
        ]
        self.rows = [
            ft.DataRow(
                [self._get_cell(cell) for cell in row],
                on_select_changed=self.callbacks.on_select_changed_row,
                on_long_press=self.callbacks.on_long_press_row,
            )
            for row in self._model.rows()
        ]
        if self.page:
            self.page.update()

    def _get_cell(self, text: str) -> ft.DataCell:
        return ft.DataCell(
            ft.Text(text),
            on_long_press=self.callbacks.on_long_press_cell,
            on_tap=self.callbacks.on_tap_cell,
            on_double_tap=self.callbacks.on_double_tap_cell,
            on_tap_cancel=self.callbacks.on_tap_cancel_cell,
            on_tap_down=self.callbacks.on_tap_down_cell,
        )


def main(page: ft.Page):
    model = polars.read_csv(
        file="https://raw.githubusercontent.com/iron3oxide/ndcc/main/ndcc/data/charts.csv",
        infer_schema_length=300,
    )
    table_config = DataTableConfig(show_checkbox_column=True, expand=True)
    callback_config = TableCallbackConfig(on_select_changed_row=lambda: print("click"))
    table = ModelDataTable(
        model=model, table_config=table_config, call_back_config=callback_config
    )
    page.scroll = ft.ScrollMode.ADAPTIVE
    page.add(ft.Column(controls=[table]))
    page.update()


ft.app(target=main)

Error message

Unhandled error processing page session : Traceback (most recent call last):
  File "/home/jason/PycharmProjects/fletched/.venv/lib/python3.11/site-packages/flet/flet.py", line 300, in on_session_created
    session_handler(page)
  File "/home/jason/PycharmProjects/fletched/fletched/controls/datatable.py", line 142, in main
    table = ModelDataTable(
            ^^^^^^^^^^^^^^^
  File "/home/jason/PycharmProjects/fletched/fletched/controls/datatable.py", line 90, in __init__
    self.model = model
    ^^^^^^^^^^
  File "/home/jason/PycharmProjects/fletched/fletched/controls/datatable.py", line 102, in model
    self._render_model()
  File "/home/jason/PycharmProjects/fletched/fletched/controls/datatable.py", line 105, in _render_model
    self.columns = [
                   ^
  File "/home/jason/PycharmProjects/fletched/fletched/controls/datatable.py", line 106, in <listcomp>
    ft.DataColumn(ft.Text(column), on_sort=self.callbacks.on_sort_column)
                                           ^^^^^^^^^^^^^^
AttributeError: 'ModelDataTable' object has no attribute 'callbacks'

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

[iron3oxide]

Nevermind, found my mistake 🤦‍♂️. For those interested: I called the model property before I set the callbacks instance variable, so of course the attribute was unknown. Also I had to move the super().__init__() call to the top so the property would have a page attribute to access. Silly me...