fix update styles (#3860)

* fix update styles

* snapshot test, version bump

* changelog

* snapshot

Author: willmcgugan

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+
+## [0.45.1] - 2023-12-12
+
+### Fixed
+
+- Fixed issues were styles wouldn't update if changed in mount. https://github.com/Textualize/textual/pull/3860
+
 ## [0.45.0] - 2023-12-12
 
 ### Fixed

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "textual"
-version = "0.45.0"
+version = "0.45.1"
 homepage = "https://github.com/Textualize/textual"
 repository = "https://github.com/Textualize/textual"
 documentation = "https://textual.textualize.io/"

src/textual/dom.py

@@ -1209,11 +1209,10 @@ def _update_styles(self) -> None:
 
         Should be called whenever CSS classes / pseudo classes change.
         """
-        if self._is_mounted:
-            try:
-                self.app.update_styles(self)
-            except NoActiveAppError:
-                pass
+        try:
+            self.app.update_styles(self)
+        except NoActiveAppError:
+            pass
 
     def add_class(self, *class_names: str, update: bool = True) -> Self:
         """Add class names to this Node.