Switching screen when a worker thread finishes it's work?

[asperand]

Hi all. I am very new to Textual and learning the ins and outs. I am a bit stuck here, and I'm wondering if I'm misunderstanding the patterns of workers and screens. Here's my code so far:

from textual.app import App, ComposeResult
from textual.widgets import Footer, Header, Input, LoadingIndicator, Label
from textual.screen import Screen
from textual.message import Message
import roster
from pathlib import Path

TITLE = "rosterget"
VERSION = "v0.1"

class RosterApp(App):
    CSS_PATH = "roster.tcss"

    def compose(self) -> ComposeResult:
        yield Header()
        yield Input(placeholder="Enter path to .xlsx file...")
    
    def on_mount(self) -> None:
        self.title = TITLE
        self.sub_title = VERSION
    
    async def on_input_submitted(self, message:Input.Submitted) -> None:
        input_box = self.query_one(Input)
        self.run_worker(self.load_excel(input_box.value),exclusive=True,thread=True)
        # Spawned our worker thread. Switch the UI over to our loading screen to show the user we're working.
        self.push_screen(LoadingScreen())
        # This loading screen works perfectly while the background work is going!

    async def load_excel(self,path:str):
        self.loaded_table = roster.RosterTable(Path(path))
        self.title = "Loaded " + str(self.loaded_table.get_row_count()) + " Rows"
        self.sub_title = TITLE + " " + VERSION
        # Despite the loading screen looking great, we're stuck on that screen.
        # I've tried screen_push(), which causes the app to close.
        # I've tried screen_switch(), which causes the app to freeze.
        # Would I have to do this in the above async function?
        # Or, would I have to create something within the LoadingScreen class to handle the worker thread completing it's work?
        
class LoadingScreen(Screen):
    def compose(self) -> ComposeResult:
        yield Header()
        yield LoadingIndicator()

class QueryScreen(Screen):
    def compose(self) -> ComposeResult:
        yield Header()
        yield Label("Finished!")

if __name__ == "__main__":
    app = RosterApp()
    app.run()

I added some comments where I'm tripped up. I am assuming I'm using the concept of screens incorrectly. I'd like to be able to switch to a new UI when the spreadsheet is loaded so that the user can complete queries through widgets within the loaded workbook.

Thanks!

[TomJGooding]

You should avoid calling methods on your UI directly from a threaded worker - use call_from_thread or custom messages for multiple updates.

https://textual.textualize.io/guide/workers/#thread-workers

[asperand]

Simple as. Thank you!