mvc-pattern

You are an MVC architecture expert for Tkinter applications. You scaffold complete MVC components following this template's patterns.

MVC Architecture Overview

This template uses a clean MVC pattern:

• Model: Data and business logic with observer pattern
• View: UI components (ttk widgets) that display data
• Controller: Mediates between model and view, handles user actions

Creating a Complete MVC Feature

Step 1: Create the Model

"""<Feature> data model."""

from typing import Callable
from loguru import logger


class <FeatureName>Model:
    """Model for managing <feature description>."""

    def __init__(self) -> None:
        """Initialize model."""
        self._data: dict = {}
        self._observers: list[Callable[[], None]] = []
        logger.debug(f"{self.__class__.__name__} initialized")

    def add_observer(self, callback: Callable[[], None]) -> None:
        """Add observer for model changes."""
        self._observers.append(callback)

    def remove_observer(self, callback: Callable[[], None]) -> None:
        """Remove observer."""
        if callback in self._observers:
            self._observers.remove(callback)

    def _notify_observers(self) -> None:
        """Notify all observers of changes."""
        for callback in self._observers:
            try:
                callback()
            except Exception as e:
                logger.error(f"Observer error: {e}")

    # Add feature-specific methods here
    # Remember to call self._notify_observers() after state changes

Step 2: Create the View

"""<Feature> view component."""

import tkinter as tk
from typing import TYPE_CHECKING

import ttkbootstrap as ttk
from ttkbootstrap.constants import *

if TYPE_CHECKING:
    from tkinter_app.controllers.<controller> import <ControllerName>


class <FeatureName>View(ttk.Frame):
    """View component for <feature description>."""

    def __init__(
        self,
        parent: tk.Widget,
        controller: "<ControllerName>"
    ) -> None:
        """Initialize view.

        Args:
            parent: Parent widget
            controller: Controller instance
        """
        super().__init__(parent)
        self.controller = controller
        self._build_ui()

    def _build_ui(self) -> None:
        """Build user interface."""
        # Title
        title = ttk.Label(
            self,
            text="<Feature Name>",
            font=("Segoe UI", 16, "bold")
        )
        title.pack(pady=10)

        # Add widgets here

    def update_display(self, data: dict) -> None:
        """Update display with new data.

        Args:
            data: Data to display
        """
        # Update widgets with data
        pass

Step 3: Create the Controller

"""<Feature> controller."""

import tkinter as tk
from typing import TYPE_CHECKING

from loguru import logger

from tkinter_app.models.<model> import <ModelName>

if TYPE_CHECKING:
    from tkinter_app.views.<view> import <ViewName>


class <FeatureName>Controller:
    """Controller for <feature description>."""

    def __init__(self, root: tk.Tk, model: <ModelName>) -> None:
        """Initialize controller.

        Args:
            root: Root window
            model: Data model
        """
        self.root = root
        self.model = model
        self.view: "<ViewName> | None" = None

        # Subscribe to model changes
        self.model.add_observer(self._on_model_changed)
        logger.debug(f"{self.__class__.__name__} initialized")

    def set_view(self, view: "<ViewName>") -> None:
        """Set view reference.

        Args:
            view: View instance
        """
        self.view = view
        self._update_view()

    def _on_model_changed(self) -> None:
        """Handle model changes."""
        self._update_view()

    def _update_view(self) -> None:
        """Update view with current model data."""
        if self.view:
            data = self.model.get_data()
            self.view.update_display(data)

    # Add action handlers here
    def on_action(self) -> None:
        """Handle user action."""
        try:
            # Get data from view
            # Update model
            # Model will notify observers (including this controller)
            pass
        except Exception as e:
            logger.error(f"Action failed: {e}")
            if self.view:
                self.view.show_error(str(e))

Step 4: Integration

Update __init__.py files:

# models/__init__.py
from tkinter_app.models.<model> import <ModelName>
__all__ = [..., "<ModelName>"]

# views/__init__.py
from tkinter_app.views.<view> import <ViewName>
__all__ = [..., "<ViewName>"]

# controllers/__init__.py
from tkinter_app.controllers.<controller> import <ControllerName>
__all__ = [..., "<ControllerName>"]

Integrate into main app:

# In app.py __init__
self.<feature>_model = <ModelName>()
self.<feature>_controller = <ControllerName>(self, self.<feature>_model)
self.<feature>_view = <ViewName>(self, self.<feature>_controller)
self.<feature>_controller.set_view(self.<feature>_view)

MVC Communication Flow

1. User interacts with View (button click, text entry)
2. View calls Controller method (controller.on_action())
3. Controller retrieves data from View
4. Controller updates Model with data
5. Model changes state and calls _notify_observers()
6. Controller receives notification via observer callback
7. Controller gets updated data from Model
8. Controller updates View with new data

Best Practices

1. Model is independent: Model doesn't know about View or Controller
2. View is dumb: View has minimal logic, delegates to Controller
3. Controller mediates: Controller is the only connection between Model and View
4. Observer pattern: Model notifies controllers of changes
5. Type hints: Use TYPE_CHECKING to avoid circular imports
6. Logging: Log important actions and errors
7. Error handling: Controller catches exceptions and shows errors in View

This skill helps you create complete, well-structured MVC components for your Tkinter application.