Struct multiversx_sc::storage::mappers::SingleValueMapper

pub struct SingleValueMapper<SA, T>
where
    SA: StorageMapperApi,
    T: TopEncode + TopDecode + 'static,
{ /* private fields */ }

Manages a single serializable item in storage.

Implementations

impl<SA, T> SingleValueMapper<SA, T>

where SA: StorageMapperApi, T: TopEncode + TopDecode,

pub fn get(&self) -> T

Retrieves current value from storage.

pub fn get_from_address(&self, address: &ManagedAddress<SA>) -> T

Gets the value from the given address. Both adresses have to be in the same shard.

pub fn is_empty(&self) -> bool

Returns whether the storage managed by this mapper is empty.

pub fn is_empty_at_address(&self, address: &ManagedAddress<SA>) -> bool

Returns whether the storage at the given key is empty at the given address. Both adresses have to be in the same shard.

pub fn set<BT>(&self, new_value: BT)

where BT: Borrow<T>,

Saves argument to storage.

Accepts owned item of type T, or any borrowed form of it, such as &T.

pub fn set_if_empty<BT>(&self, value: BT)

where BT: Borrow<T>,

Saves argument to storage only if the storage is empty. Does nothing otherwise.

pub fn clear(&self)

Clears the storage for this mapper.

pub fn update<R, F: FnOnce(&mut T) -> R>(&self, f: F) -> R

Syntactic sugar, to more compactly express a get, update and set in one line. Takes whatever lies in storage, apples the given closure and saves the final value back to storage. Propagates the return value of the given function.

pub fn raw_byte_length(&self) -> usize

pub fn take(&self) -> T

Takes the value out of the storage, clearing it in the process.

pub fn replace<BT>(&self, new_value: BT) -> T

where BT: Borrow<T>,

Trait Implementations

impl<SA, T> StorageMapper<SA> for SingleValueMapper<SA, T>

where SA: StorageMapperApi, T: TopEncode + TopDecode,

fn new(base_key: StorageKey<SA>) -> Self

Will be called automatically by the #[storage_mapper] annotation generated code.

impl<SA, T> TopEncodeMulti for SingleValueMapper<SA, T>

where SA: StorageMapperApi, T: TopEncode + TopDecode,

fn multi_encode_or_handle_err<O, H>( &self, output: &mut O, h: H ) -> Result<(), H::HandledErr>

where O: TopEncodeMultiOutput, H: EncodeErrorHandler,

Version of top_encode that can handle errors as soon as they occur. For instance in can exit immediately and make sure that if it returns, it is a success. By not deferring error handling, this can lead to somewhat smaller bytecode.

fn multi_encode<O>(&self, output: &mut O) -> Result<(), EncodeError>

where O: TopEncodeMultiOutput,

Attempt to serialize the value to ouput.

impl<SA, T> TypeAbi for SingleValueMapper<SA, T>

where SA: StorageMapperApi, T: TopEncode + TopDecode + TypeAbi,

fn type_name() -> TypeName

fn provide_type_descriptions<TDC: TypeDescriptionContainer>( accumulator: &mut TDC )

A type can provide more than its own name. For instance, a struct can also provide the descriptions of the type of its fields. TypeAbi doesn’t care for the exact accumulator type, which is abstracted by the TypeDescriptionContainer trait.

impl<SA, T> CodecFrom<SingleValueMapper<SA, T>> for PlaceholderOutput

where SA: StorageMapperApi, T: TopEncode + TopDecode,

impl<SA, T, R> CodecFrom<SingleValueMapper<SA, T>> for SingleValue<R>

where SA: StorageMapperApi, T: TopEncode + TopDecode, R: TopDecode + CodecFrom<T>,

impl<SA, T> !CodecFromSelf for SingleValueMapper<SA, T>

where SA: StorageMapperApi, T: TopEncode + TopDecode,