Trait settings_storage::device_storage::DeviceStorageConvertible

source ·

pub trait DeviceStorageConvertible: Sized {
    type Storable: DeviceStorageCompatible + Into<Self>;

    // Required method
    fn get_storable(&self) -> Cow<'_, Self::Storable>;
}

Expand description

This trait represents types that can be converted into a storable type. It’s also important that the type it is transformed into can also be converted back into this type. This reverse conversion is used to populate the fields of the original type with the stored values plus defaulting the other fields that, e.g. might later be populated from hardware APIs.

§Example

// Struct used in controllers.
struct SomeSettingInfo {
    storable_field: u8,
    hardware_backed_field: String,
}

// Struct only used for storage.
#[derive(Serialize, Deserialize, PartialEq, Clone)]
struct StorableSomeSettingInfo {
    storable_field: u8,
}

// Impl compatible for the storable type.
impl DeviceStorageCompatible for StorableSomeSettingInfo {
    const KEY: &'static str = "some_setting_info";

    fn default_value() -> Self {
        Self { storable_field: 1, }
    }
}

// Impl convertible for controller type.
impl DeviceStorageConvertible for SomeSettingInfo {
    type Storable = StorableSomeSettingInfo;
    fn get_storable(&self) -> Cow<'_, Self::Storable> {
        Cow::Owned(Self {
            storable_field: self.storable_field,
            hardware_backed_field: String::new()
        })
    }
}

// This impl helps us convert from the storable version to the
// controller version of the struct. Hardware fields should be backed
// by default or usable values.
impl Into<SomeSettingInfo> for StorableSomeSettingInfo {
    fn into(self) -> SomeSettingInfo {
        SomeSettingInfo {
            storable_field: self.storable_field,
            hardware_backed_field: String::new(),
        }
    }
}