1 files changed, 26 insertions, 2 deletions
diff --git a/tedge_config/src/config_setting.rs b/tedge_config/src/config_setting.rs
index c34d1fc9..fde2c46c 100644
--- a/tedge_config/src/config_setting.rs
+++ b/tedge_config/src/config_setting.rs
@@ -27,6 +27,24 @@ pub trait ConfigSettingAccessor<T: ConfigSetting> {
     fn unset(&mut self, _setting: T) -> ConfigSettingResult<()>;
 }
 
+/// Extension trait that provides methods to query a setting as a String or
+/// update a setting provided a String value.
+pub trait ConfigSettingAccessorStringExt<T: ConfigSetting>: ConfigSettingAccessor<T> {
+    /// Read a configuration setting and convert it into a String.
+    fn query_string(&self, setting: T) -> ConfigSettingResult<String>;
+
+    fn query_string_optional(&self, setting: T) -> ConfigSettingResult<Option<String>> {
+        match self.query_string(setting) {
+            Ok(value) => Ok(Some(value)),
+            Err(ConfigSettingError::ConfigNotSet { .. }) => Ok(None),
+            Err(err) => Err(err),
+        }
+    }
+
+    /// Update a configuration setting from a String value
+    fn update_string(&mut self, setting: T, value: String) -> ConfigSettingResult<()>;
+}
+
 pub type ConfigSettingResult<T> = Result<T, ConfigSettingError>;
 
 #[derive(thiserror::Error, Debug)]
@@ -37,6 +55,12 @@ pub enum ConfigSettingError {
     )]
     ConfigNotSet { key: &'static str },
 
-    #[error("Readonly setting")]
-    ReadonlySetting,
+    #[error("Readonly setting: {message}")]
+    ReadonlySetting { message: &'static str },
+
+    #[error("Conversion from String failed")]
+    ConversionFromStringFailed,
+
+    #[error("Conversion into String failed")]
+    ConversionIntoStringFailed,
 }