diff --git a/src/entity/active_model.rs b/src/entity/active_model.rs index 587e6ee8a..7d07f5972 100644 --- a/src/entity/active_model.rs +++ b/src/entity/active_model.rs @@ -851,6 +851,43 @@ where }; } + /// `Set(value)`, except when [`self.is_unchanged()`][ActiveValue#method.is_unchanged] + /// and `value` equals the current [Unchanged][ActiveValue::Unchanged] value. + /// + /// This is useful when you have an [Unchanged][ActiveValue::Unchanged] value from the database, + /// then update it using this method, + /// and then use [`.is_unchanged()`][ActiveValue#method.is_unchanged] to see whether it has *actually* changed. + /// + /// The same nice effect applies to the entire `ActiveModel`. + /// You can now meaningfully use [ActiveModelTrait::is_changed][ActiveModelTrait#method.is_changed] + /// to see whether are any changes that need to be saved to the database. + /// + /// ## Examples + /// + /// ``` + /// # use sea_orm::ActiveValue; + /// # + /// let mut value = ActiveValue::Unchanged("old"); + /// + /// // This wouldn't be the case if we used plain `value = Set("old");` + /// value.set_if_not_equals("old"); + /// assert!(value.is_unchanged()); + /// + /// // Only when we change the actual `&str` value, it becomes `Set` + /// value.set_if_not_equals("new"); + /// assert_eq!(value.is_unchanged(), false); + /// assert_eq!(value, ActiveValue::Set("new")); + /// ``` + pub fn set_if_not_equals(&mut self, value: V) + where + V: PartialEq, + { + match self { + ActiveValue::Unchanged(current) if &value == current => {} + _ => *self = ActiveValue::Set(value), + } + } + /// Get the inner value, unless `self` is [NotSet][ActiveValue::NotSet]. /// /// There's also a panicking version: [ActiveValue::as_ref].