Add LocalizedRef expression for extracting the value in the current language

localized_fields/expressions.py

@@ -0,0 +1,25 @@
+from django.conf import settings
+from django.utils import translation
+
+from psqlextra import expressions
+
+
+class LocalizedRef(expressions.HStoreRef):
+    """Expression that selects the value in a field only in
+    the currently active language."""
+
+    def __init__(self, name: str, lang: str=None):
+        """Initializes a new instance of :see:LocalizedRef.
+
+        Arguments:
+            name:
+                The field/column to select from.
+
+            lang:
+                The language to get the field/column in.
+                If not specified, the currently active language
+                is used.
+        """
+
+        language = lang or translation.get_language() or settings.LANGUAGE_CODE
+        super().__init__(name, language)