pub trait StorageMap<K, V>where
    K: FullEncode,
    V: FullCodec,{
    type Query;
Show 17 methods
    fn hashed_key_for<KeyArg>(key: KeyArg) -> Vec<u8, Global> ⓘ
    where
        KeyArg: EncodeLike<K>;
    fn contains_key<KeyArg>(key: KeyArg) -> bool
    where
        KeyArg: EncodeLike<K>;
    fn get<KeyArg>(key: KeyArg) -> Self::Query
    where
        KeyArg: EncodeLike<K>;
    fn set<KeyArg>(key: KeyArg, query: Self::Query)
    where
        KeyArg: EncodeLike<K>;
    fn try_get<KeyArg>(key: KeyArg) -> Result<V, ()>
    where
        KeyArg: EncodeLike<K>;
    fn swap<KeyArg1, KeyArg2>(key1: KeyArg1, key2: KeyArg2)
    where
        KeyArg1: EncodeLike<K>,
        KeyArg2: EncodeLike<K>;
    fn insert<KeyArg, ValArg>(key: KeyArg, val: ValArg)
    where
        KeyArg: EncodeLike<K>,
        ValArg: EncodeLike<V>;
    fn remove<KeyArg>(key: KeyArg)
    where
        KeyArg: EncodeLike<K>;
    fn mutate<KeyArg, R, F>(key: KeyArg, f: F) -> R
    where
        KeyArg: EncodeLike<K>,
        F: FnOnce(&mut Self::Query) -> R;
    fn try_mutate<KeyArg, R, E, F>(key: KeyArg, f: F) -> Result<R, E>
    where
        KeyArg: EncodeLike<K>,
        F: FnOnce(&mut Self::Query) -> Result<R, E>;
    fn mutate_exists<KeyArg, R, F>(key: KeyArg, f: F) -> R
    where
        KeyArg: EncodeLike<K>,
        F: FnOnce(&mut Option<V>) -> R;
    fn try_mutate_exists<KeyArg, R, E, F>(key: KeyArg, f: F) -> Result<R, E>
    where
        KeyArg: EncodeLike<K>,
        F: FnOnce(&mut Option<V>) -> Result<R, E>;
    fn take<KeyArg>(key: KeyArg) -> Self::Query
    where
        KeyArg: EncodeLike<K>;
    fn append<Item, EncodeLikeItem, EncodeLikeKey>(
        key: EncodeLikeKey,
        item: EncodeLikeItem
    )
    where
        EncodeLikeKey: EncodeLike<K>,
        Item: Encode,
        EncodeLikeItem: EncodeLike<Item>,
        V: StorageAppend<Item>;
    fn migrate_key<OldHasher, KeyArg>(key: KeyArg) -> Option<V>
    where
        OldHasher: StorageHasher,
        KeyArg: EncodeLike<K>;
    fn decode_len<KeyArg>(key: KeyArg) -> Option<usize>
    where
        KeyArg: EncodeLike<K>,
        V: StorageDecodeLength,
    { ... }
    fn migrate_key_from_blake<KeyArg>(key: KeyArg) -> Option<V>
    where
        KeyArg: EncodeLike<K>,
    { ... }
}Expand description
A strongly-typed map in storage.
Details on implementation can be found at [generator::StorageMap].
Required Associated Types§
type Query
type Query
The type that get/take return.
Required Methods§
fn hashed_key_for<KeyArg>(key: KeyArg) -> Vec<u8, Global> ⓘwhere
    KeyArg: EncodeLike<K>,
fn hashed_key_for<KeyArg>(key: KeyArg) -> Vec<u8, Global> ⓘwhere
    KeyArg: EncodeLike<K>,
Get the storage key used to fetch a value corresponding to a specific key.
fn contains_key<KeyArg>(key: KeyArg) -> boolwhere
    KeyArg: EncodeLike<K>,
fn contains_key<KeyArg>(key: KeyArg) -> boolwhere
    KeyArg: EncodeLike<K>,
Does the value (explicitly) exist in storage?
fn get<KeyArg>(key: KeyArg) -> Self::Querywhere
    KeyArg: EncodeLike<K>,
fn get<KeyArg>(key: KeyArg) -> Self::Querywhere
    KeyArg: EncodeLike<K>,
Load the value associated with the given key from the map.
fn set<KeyArg>(key: KeyArg, query: Self::Query)where
    KeyArg: EncodeLike<K>,
fn set<KeyArg>(key: KeyArg, query: Self::Query)where
    KeyArg: EncodeLike<K>,
Store or remove the value to be associated with key so that get returns the query.
fn try_get<KeyArg>(key: KeyArg) -> Result<V, ()>where
    KeyArg: EncodeLike<K>,
fn try_get<KeyArg>(key: KeyArg) -> Result<V, ()>where
    KeyArg: EncodeLike<K>,
Try to get the value for the given key from the map.
Returns Ok if it exists, Err if not.
fn swap<KeyArg1, KeyArg2>(key1: KeyArg1, key2: KeyArg2)where
    KeyArg1: EncodeLike<K>,
    KeyArg2: EncodeLike<K>,
fn swap<KeyArg1, KeyArg2>(key1: KeyArg1, key2: KeyArg2)where
    KeyArg1: EncodeLike<K>,
    KeyArg2: EncodeLike<K>,
Swap the values of two keys.
fn insert<KeyArg, ValArg>(key: KeyArg, val: ValArg)where
    KeyArg: EncodeLike<K>,
    ValArg: EncodeLike<V>,
fn insert<KeyArg, ValArg>(key: KeyArg, val: ValArg)where
    KeyArg: EncodeLike<K>,
    ValArg: EncodeLike<V>,
Store a value to be associated with the given key from the map.
fn remove<KeyArg>(key: KeyArg)where
    KeyArg: EncodeLike<K>,
fn remove<KeyArg>(key: KeyArg)where
    KeyArg: EncodeLike<K>,
Remove the value under a key.
fn mutate<KeyArg, R, F>(key: KeyArg, f: F) -> Rwhere
    KeyArg: EncodeLike<K>,
    F: FnOnce(&mut Self::Query) -> R,
fn mutate<KeyArg, R, F>(key: KeyArg, f: F) -> Rwhere
    KeyArg: EncodeLike<K>,
    F: FnOnce(&mut Self::Query) -> R,
Mutate the value under a key.
fn try_mutate<KeyArg, R, E, F>(key: KeyArg, f: F) -> Result<R, E>where
    KeyArg: EncodeLike<K>,
    F: FnOnce(&mut Self::Query) -> Result<R, E>,
fn try_mutate<KeyArg, R, E, F>(key: KeyArg, f: F) -> Result<R, E>where
    KeyArg: EncodeLike<K>,
    F: FnOnce(&mut Self::Query) -> Result<R, E>,
Mutate the item, only if an Ok value is returned.
fn mutate_exists<KeyArg, R, F>(key: KeyArg, f: F) -> Rwhere
    KeyArg: EncodeLike<K>,
    F: FnOnce(&mut Option<V>) -> R,
fn mutate_exists<KeyArg, R, F>(key: KeyArg, f: F) -> Rwhere
    KeyArg: EncodeLike<K>,
    F: FnOnce(&mut Option<V>) -> R,
Mutate the value under a key.
Deletes the item if mutated to a None.
fn try_mutate_exists<KeyArg, R, E, F>(key: KeyArg, f: F) -> Result<R, E>where
    KeyArg: EncodeLike<K>,
    F: FnOnce(&mut Option<V>) -> Result<R, E>,
fn try_mutate_exists<KeyArg, R, E, F>(key: KeyArg, f: F) -> Result<R, E>where
    KeyArg: EncodeLike<K>,
    F: FnOnce(&mut Option<V>) -> Result<R, E>,
Mutate the item, only if an Ok value is returned. Deletes the item if mutated to a None.
f will always be called with an option representing if the storage item exists (Some<V>)
or if the storage item does not exist (None), independent of the QueryType.
fn take<KeyArg>(key: KeyArg) -> Self::Querywhere
    KeyArg: EncodeLike<K>,
fn take<KeyArg>(key: KeyArg) -> Self::Querywhere
    KeyArg: EncodeLike<K>,
Take the value under a key.
fn append<Item, EncodeLikeItem, EncodeLikeKey>(
    key: EncodeLikeKey,
    item: EncodeLikeItem
)where
    EncodeLikeKey: EncodeLike<K>,
    Item: Encode,
    EncodeLikeItem: EncodeLike<Item>,
    V: StorageAppend<Item>,
fn append<Item, EncodeLikeItem, EncodeLikeKey>(
    key: EncodeLikeKey,
    item: EncodeLikeItem
)where
    EncodeLikeKey: EncodeLike<K>,
    Item: Encode,
    EncodeLikeItem: EncodeLike<Item>,
    V: StorageAppend<Item>,
Append the given items to the value in the storage.
V is required to implement codec::EncodeAppend.
Warning
If the storage item is not encoded properly, the storage will be overwritten
and set to [item]. Any default value set for the storage item will be ignored
on overwrite.
fn migrate_key<OldHasher, KeyArg>(key: KeyArg) -> Option<V>where
    OldHasher: StorageHasher,
    KeyArg: EncodeLike<K>,
fn migrate_key<OldHasher, KeyArg>(key: KeyArg) -> Option<V>where
    OldHasher: StorageHasher,
    KeyArg: EncodeLike<K>,
Migrate an item with the given key from a defunct OldHasher to the current hasher.
If the key doesn’t exist, then it’s a no-op. If it does, then it returns its value.
Provided Methods§
fn decode_len<KeyArg>(key: KeyArg) -> Option<usize>where
    KeyArg: EncodeLike<K>,
    V: StorageDecodeLength,
fn decode_len<KeyArg>(key: KeyArg) -> Option<usize>where
    KeyArg: EncodeLike<K>,
    V: StorageDecodeLength,
Read the length of the storage value without decoding the entire value under the
given key.
V is required to implement StorageDecodeLength.
If the value does not exists or it fails to decode the length, None is returned.
Otherwise Some(len) is returned.
Warning
None does not mean that get() does not return a value. The default value is completly
ignored by this function.
fn migrate_key_from_blake<KeyArg>(key: KeyArg) -> Option<V>where
    KeyArg: EncodeLike<K>,
fn migrate_key_from_blake<KeyArg>(key: KeyArg) -> Option<V>where
    KeyArg: EncodeLike<K>,
Migrate an item with the given key from a blake2_256 hasher to the current hasher.
If the key doesn’t exist, then it’s a no-op. If it does, then it returns its value.