Struct cw_storage_plus::SnapshotItem

pub struct SnapshotItem<'a, T> { /* fields omitted */ }

Item that maintains a snapshot of one or more checkpoints. We can query historical data as well as current state. What data is snapshotted depends on the Strategy.

Implementations

impl<'a, T> SnapshotItem<'a, T>

pub const fn new(
    storage_key: &'a str,
    checkpoints: &'a str,
    changelog: &'a str,
    strategy: Strategy
) -> Self

Example:

use cw_storage_plus::{SnapshotItem, Strategy};

SnapshotItem::<'static, u64>::new(
    "every",
    "every__check",
    "every__change",
    Strategy::EveryBlock);

pub fn add_checkpoint(
    &self,
    store: &mut dyn Storage,
    height: u64
) -> StdResult<()>

pub fn remove_checkpoint(
    &self,
    store: &mut dyn Storage,
    height: u64
) -> StdResult<()>

impl<'a, T> SnapshotItem<'a, T> where
    T: Serialize + DeserializeOwned + Clone, 

pub fn save(
    &self,
    store: &mut dyn Storage,
    data: &T,
    height: u64
) -> StdResult<()>

pub fn remove(&self, store: &mut dyn Storage, height: u64) -> StdResult<()>

pub fn load(&self, store: &dyn Storage) -> StdResult<T>

load will return an error if no data is set, or on parse error

pub fn may_load(&self, store: &dyn Storage) -> StdResult<Option<T>>

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

pub fn may_load_at_height(
    &self,
    store: &dyn Storage,
    height: u64
) -> StdResult<Option<T>>

pub fn assert_checkpointed(
    &self,
    store: &dyn Storage,
    height: u64
) -> StdResult<()>

pub fn update<A, E>(
    &self,
    store: &mut dyn Storage,
    height: u64,
    action: A
) -> Result<T, E> where
    A: FnOnce(Option<T>) -> Result<T, E>,
    E: From<StdError>, 

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

If the data exists, action(Some(value)) is called. Otherwise action(None) is called.

This is a bit more customized than needed to only read “old” value 1 time, not 2 per naive approach