Struct concordium_std::OccupiedEntry

pub struct OccupiedEntry<'a, K, V: Serial, S: HasStateApi> { /* private fields */ }

A view into an occupied entry in a StateMap. It can be obtained via the StateMap::entry method. This allows looking up or modifying the value at a give key in-place.

The type implements DerefMut which allows the value to be mutated. The Drop implementation ensures that the value is properly stored in the contract state maintained by the node.

This differs from OccupiedEntryRaw in that this automatically handles serialization and provides convenience methods for modifying the value via the DerefMut implementation.

Implementations

impl<'a, K, V, StateApi> OccupiedEntry<'a, K, V, StateApi> where
    K: Serial,
    V: Serial,
    StateApi: HasStateApi, 

pub fn key(&self) -> &K

Get a reference to the key that is associated with this entry.

pub fn get_ref(&self) -> &V

Get an immutable reference to the value contained in this entry.

pub fn modify<F, A>(&mut self, f: F) -> A where
    F: FnOnce(&mut V) -> A, 

Modify the value in the entry, and possibly return some information.

pub fn try_modify<F, A, E>(&mut self, f: F) -> Result<A, E> where
    F: FnOnce(&mut V) -> Result<A, E>, 

Like modify, but allows the closure to signal failure, aborting the update.

Trait Implementations

impl<'a, K, V: Serial, S: HasStateApi> Deref for OccupiedEntry<'a, K, V, S>

type Target = V

The resulting type after dereferencing.

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

Dereferences the value.

impl<'a, K, V: Serial, S: HasStateApi> DerefMut for OccupiedEntry<'a, K, V, S>

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<'a, K, V: Serial, S: HasStateApi> Drop for OccupiedEntry<'a, K, V, S>

fn drop(&mut self)

Executes the destructor for this type.