create advanced_filter_controller

core/lib/core.dart

@@ -33,6 +33,7 @@ export 'utils/benchmark.dart';
 export 'utils/fps_manager.dart';
 export 'utils/build_utils.dart';
 export 'utils/wrapper.dart';
+export 'utils/string_convert.dart';
 
 // Views
 export 'presentation/views/text/slogan_builder.dart';

core/lib/utils/string_convert.dart

@@ -0,0 +1,10 @@
+class StringConvert {
+ static String? writeEmptyToNull(String text) {
+    if (text.isEmpty) return null;
+    return text;
+  }
+
+ static String writeNullToEmpty(String? text) {
+    return text ?? '';
+  }
+}