How to store state in App?

[chbndrhnns]

Is there a good place to store context or state within a textual app?
I’d like to keep some business logic separate from the handler and action methods but want to access it from within these methods.

[TomJGooding]

This question is so broad it is difficult to offer any meaningful or practical advice. Could you try narrowing down your question, perhaps with a simple example?

[chbndrhnns]

I'd like to inject custom state when creating the app instance.

Here is a simple example where I am just setting an arbitrary attribute on the app after creating it.
This breaks typing information as no part of the application is aware of that additional attribute.

Is there a better way to do it?

import pytest
from textual.app import App, ComposeResult
from textual.widgets import Button


class State:
    def __init__(self):
        self.count = 0


class MyUi(App):
    def compose(self) -> ComposeResult:
        yield Button("Default", id="default")

    def on_button_pressed(self, event: Button.Pressed) -> None:
        self.my_state.count += 1


@pytest.fixture(autouse=True)
def anyio_backend():
    return "asyncio"


async def test_():
    state = State()
    app = MyUi()
    app.my_state = state

    async with app.run_test() as pilot:
        await pilot.click("#default")

    assert state.count == 1

[davep]

This breaks typing information as no part of the application is aware of that additional attribute.

Your app is simply a Python class, so you can "declare" that attribute as you generally would with any other Python class: create/assign/type the attribute in __init__ (just like you did in your State class).

[daddycocoaman]

@davep Hi, I see this was marked as answered but I don't think it solves the intent here. You can still create/assign/type stuff to the app, but when you call something like self.app from the app, it returns an App[object] type, and not the actual app (in this case MyUi which has an additional attribute). So any use of self.app won't see that additional attribute, unless you explicitly type that as self.app: MyUi. But this breaks of convenience of trying to access self.app.my_state for typing.

Would it be possible to use something like AppType = NewType(<actual App class name>, App) when the app contextvar gets set and return AppType instead of App[object]?

[davep]

The person asking the question marked it as answered, not me. I would assume they were confident that their question was satisfied by the answer(s).

Feel free to ask your unsatisfied question as a new discussion.

[daddycocoaman]

Alternatively, and probably way easier, a context dict subclass would also work with a custom get(name, type, default) function that also accepts a type, and returns that type. So in this case, something like self.app.context.get("my_state", int, None) would be useful.