Struct cache_loader_async::cache_api::LoadingCache

pub struct LoadingCache<K, V, E: Debug> { /* fields omitted */ }

Implementations

impl<K: Eq + Hash + Clone + Send + 'static, V: Clone + Sized + Send + 'static, E: Clone + Sized + Send + Debug + 'static> LoadingCache<K, V, E>

pub fn new<T, F>(loader: T) -> (LoadingCache<K, V, E>, CacheHandle) where
    F: Future<Output = Result<V, E>> + Sized + Send + 'static,
    T: Fn(K) -> F + Send + 'static, 

Creates a new instance of a LoadingCache with the default HashMapBacking

Arguments

• loader - A function which returns a Future<Output=Option>

Return Value

This method returns a tuple, with: 0 - The instance of the LoadingCache 1 - The CacheHandle which is a JoinHandle<()> and represents the task which operates the cache

Examples

use cache_loader_async::cache_api::LoadingCache;
use std::collections::HashMap;
async fn example() {
    let static_db: HashMap<String, u32> =
        vec![("foo".into(), 32), ("bar".into(), 64)]
            .into_iter()
            .collect();

    let (cache, _) = LoadingCache::new(move |key: String| {
        let db_clone = static_db.clone();
        async move {
            db_clone.get(&key).cloned().ok_or(1)
        }
    });

    let result = cache.get("foo".to_owned()).await.unwrap();

    assert_eq!(result, 32);
}

pub fn with_backing<T, F, B>(
    backing: B,
    loader: T
) -> (LoadingCache<K, V, E>, CacheHandle) where
    F: Future<Output = Result<V, E>> + Sized + Send + 'static,
    T: Fn(K) -> F + Send + 'static,
    B: CacheBacking<K, CacheEntry<V, E>> + Send + 'static, 

Creates a new instance of a LoadingCache with a custom CacheBacking

Arguments

• backing - The custom backing which the cache should use
• loader - A function which returns a Future<Output=Option>

Return Value

This method returns a tuple, with: 0 - The instance of the LoadingCache 1 - The CacheHandle which is a JoinHandle<()> and represents the task which operates the cache

Examples

use cache_loader_async::cache_api::LoadingCache;
use std::collections::HashMap;
use cache_loader_async::backing::HashMapBacking;
async fn example() {
    let static_db: HashMap<String, u32> =
        vec![("foo".into(), 32), ("bar".into(), 64)]
            .into_iter()
            .collect();

    let (cache, _) = LoadingCache::with_backing(
        HashMapBacking::new(), // this is the default implementation of `new`
        move |key: String| {
            let db_clone = static_db.clone();
            async move {
                db_clone.get(&key).cloned().ok_or(1)
            }
        }
    );

    let result = cache.get("foo".to_owned()).await.unwrap();

    assert_eq!(result, 32);
}

pub async fn get(&self, key: K) -> Result<V, CacheLoadingError<E>>

Retrieves or loads the value for specified key from either cache or loader function

Arguments

• key - The key which should be loaded

Return Value

Returns a Result with: Ok - Value of type V Err - Error of type CacheLoadingError

pub async fn get_with_meta(
    &self,
    key: K
) -> Result<ResultMeta<V>, CacheLoadingError<E>>

Retrieves or loads the value for specified key from either cache or loader function with meta information, i.e. if the key was loaded from cache or from the loader function

Arguments

• key - The key which should be loaded

Return Value

Returns a Result with: Ok - Value of type ResultMeta Err - Error of type CacheLoadingError

pub async fn set(
    &self,
    key: K,
    value: V
) -> Result<Option<V>, CacheLoadingError<E>>

Sets the value for specified key and bypasses eventual currently ongoing loads If a key has been set programmatically, eventual concurrent loads will not change the value of the key.

Arguments

• key - The key which should be loaded

Return Value

Returns a Result with: Ok - Previous value of type V wrapped in an Option depending whether there was a previous value Err - Error of type CacheLoadingError

pub async fn get_if_present(
    &self,
    key: K
) -> Result<Option<V>, CacheLoadingError<E>>

Loads the value for the specified key from the cache and returns None if not present

Arguments

• key - The key which should be loaded

Return Value

Returns a Result with: Ok - Value of type Option Err - Error of type CacheLoadingError

pub async fn exists(&self, key: K) -> Result<bool, CacheLoadingError<E>>

Checks whether a specific value is mapped for the given key

Arguments

• key - The key which should be checked

Return Value

Returns a Result with: Ok - bool Err - Error of type CacheLoadingError

pub async fn remove(&self, key: K) -> Result<Option<V>, CacheLoadingError<E>>

Removes a specific key-value mapping from the cache and returns the previous result if there was any or None

Arguments

• key - The key which should be evicted

Return Value

Returns a Result with: Ok - Value of type Option Err - Error of type CacheLoadingError

pub async fn remove_if<P: Fn((&K, Option<&V>)) -> bool + Send + Sync + 'static>(
    &self,
    predicate: P
) -> Result<(), CacheLoadingError<E>>

Removes all entries which match the specified predicate

Arguments

• predicate - The predicate to test all entries against

Return Value

Returns a Result with: Ok - Nothing, the removed values are discarded Err - Error of type CacheLoadingError -> the values were not discarded

pub async fn update<U>(
    &self,
    key: K,
    update_fn: U
) -> Result<V, CacheLoadingError<E>> where
    U: FnOnce(V) -> V + Send + 'static, 

Updates a key on the cache with the given update function and returns the updated value

If the key is not present yet, it’ll be loaded using the loader function and will be updated once this loader function completes. In case the key was manually updated via set during the loader function the update will take place on the manually updated value, so user-controlled input takes precedence over the loader function

Arguments

• key - The key which should be updated
• update_fn - A FnOnce(V) -> V which has the current value as parameter and should return the updated value

Return Value

Returns a Result with: Ok - Value of type V which is the previously mapped value Err - Error of type CacheLoadingError

pub async fn update_if_exists<U>(
    &self,
    key: K,
    update_fn: U
) -> Result<Option<V>, CacheLoadingError<E>> where
    U: FnOnce(V) -> V + Send + 'static, 

Updates a key on the cache with the given update function and returns the updated value if it existed

If the key is not present yet, it’ll be ignored. This also counts for keys in LOADING state.

Arguments

• key - The key which should be updated
• update_fn - A FnOnce(V) -> V which has the current value as parameter and should return the updated value

Return Value

Returns a Result with: Ok - Optional value of type V which is the previously mapped value Err - Error of type CacheLoadingError

pub async fn update_mut<U>(
    &self,
    key: K,
    update_fn: U
) -> Result<V, CacheLoadingError<E>> where
    U: FnMut(&mut V) + Send + 'static, 

Updates a key on the cache with the given update function and returns the updated value

If the key is not present yet, it’ll be loaded using the loader function and will be updated once this loader function completes. In case the key was manually updated via set during the loader function the update will take place on the manually updated value, so user-controlled input takes precedence over the loader function

Arguments

• key - The key which should be updated
• update_fn - A FnMut(&mut V) -> () which has the current value as parameter and should update it accordingly

Return Value

Returns a Result with: Ok - Value of type V Err - Error of type CacheLoadingError

pub async fn update_mut_if_exists<U>(
    &self,
    key: K,
    update_fn: U
) -> Result<Option<V>, CacheLoadingError<E>> where
    U: FnMut(&mut V) + Send + 'static, 

Updates a key on the cache with the given update function and returns the updated value if it existed

If the key is not present yet, it’ll be ignored. Keys in LOADING state will still be updated as they get available.

Arguments

• key - The key which should be updated
• update_fn - A FnMut(&mut V) -> () which has the current value as parameter and should update it accordingly

Return Value

Returns a Result with: Ok - Optional value of type V Err - Error of type CacheLoadingError

Trait Implementations

impl<K: Clone, V: Clone, E: Clone + Debug> Clone for LoadingCache<K, V, E>

fn clone(&self) -> LoadingCache<K, V, E>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<K: Debug, V: Debug, E: Debug> Debug for LoadingCache<K, V, E>

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

Formats the value using the given formatter.