Struct fadroma::prelude::cosmwasm_storage::Singleton

pub struct Singleton<'a, S, T> where
    S: Storage,
    T: Serialize + DeserializeOwned,  { /* private fields */ }

Singleton effectively combines PrefixedStorage with TypedStorage to work on a single storage key. It performs the to_length_prefixed transformation on the given name to ensure no collisions, and then provides the standard TypedStorage accessors, without requiring a key (which is defined in the constructor)

Implementations

impl<'a, S, T> Singleton<'a, S, T> where
    S: Storage,
    T: Serialize + DeserializeOwned, 

pub fn new(storage: &'a mut S, key: &[u8]) -> Singleton<'a, S, T>

pub fn save(&mut self, data: &T) -> Result<(), StdError>

save will serialize the model and store, returns an error on serialization issues

pub fn remove(&mut self)

pub fn load(&self) -> Result<T, StdError>

load will return an error if no data is set at the given key, or on parse error

pub fn may_load(&self) -> Result<Option<T>, StdError>

may_load will parse the data stored at the key if present, returns Ok(None) if no data there. returns an error on issues parsing

pub fn update<A>(&mut self, action: A) -> Result<T, StdError> where
    A: FnOnce(T) -> Result<T, StdError>, 

update will load the data, perform the specified action, and store the result in the database. This is shorthand for some common sequences, which may be useful

This is the least stable of the APIs, and definitely needs some usage