Struct Persisted

pub struct Persisted<S, K>
where
    S: PersistedStore<K>,
    K: PersistedKey,
{ /* private fields */ }

A wrapper that will automatically persist its contained value to the store. The value will be loaded from the store on creation, and saved on mutation.

Generic Params

• S: The backend type used to persist data. While we don’t need access to an instance of the backend, we do need to know its type so we can access its static functions on setup/mutation.
• K: The type of the persistence key. The associated Value type will be the type of the contained value.

Accessing

The inner value can be accessed immutably via Deref. To get mutable access, use Persisted::get_mut. This wrapper method returns a guard that implements DerefMut (similar to RefMut or MutexGuard from std, without the internal mutability). When your mutable access is complete, this wrapper will be dropped and the value, which presumably was changed, will be persisted to the store.

Cloning

This type intentionally does not implement Clone. Cloning would result in two values with the same key. When the values are mutated, their persisted values would overwrite each other. It’s unlikely this is the desired behavior, and therefore is not provided.

Implementations

impl<S, K> Persisted<S, K>

where S: PersistedStore<K>, K: PersistedKey,

pub fn new(key: K, default: K::Value) -> Self

Initialize a new persisted value. The latest persisted value will be loaded from the store. If missing, use the given default instead.

pub fn new_default(key: K) -> Self

where K::Value: Default,

Initialize a new persisted value. The latest persisted value will be loaded from the store. If missing, use the value type’s Default implementation instead.

pub fn get_mut(&mut self) -> PersistedRefMut<'_, S, K>

Get a mutable reference to the value. This is wrapped by a guard, so that after mutation when the guard is dropped, the value can be saved.

Trait Implementations

impl<S, K> Debug for Persisted<S, K>

where S: PersistedStore<K>, K: PersistedKey + Debug, K::Value: Debug,

fn fmt(&self, __derive_more_f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<S, K> Default for Persisted<S, K>

where S: PersistedStore<K>, K: PersistedKey + Default, K::Value: Default,

fn default() -> Self

Returns the “default value” for a type.

impl<S, K> Deref for Persisted<S, K>

where S: PersistedStore<K>, K: PersistedKey,

type Target = <K as PersistedKey>::Value

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<S, K> Display for Persisted<S, K>

where S: PersistedStore<K>, K: PersistedKey, K::Value: Display,

fn fmt(&self, __derive_more_f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.