Trait frame_support::storage::StorageMap[−][src]

pub trait StorageMap<K: FullEncode, V: FullCodec> {
    type Query;

Show methods    fn hashed_key_for<KeyArg: EncodeLike<K>>(key: KeyArg) -> Vec<u8>ⓘ
Notable traits for Vec<u8, A>
impl<A> Write for Vec<u8, A> where
    A: Allocator, 
;

    fn contains_key<KeyArg: EncodeLike<K>>(key: KeyArg) -> bool;

    fn get<KeyArg: EncodeLike<K>>(key: KeyArg) -> Self::Query;

    fn try_get<KeyArg: EncodeLike<K>>(key: KeyArg) -> Result<V, ()>;

    fn swap<KeyArg1: EncodeLike<K>, KeyArg2: EncodeLike<K>>(
        key1: KeyArg1, 
        key2: KeyArg2
    );

    fn insert<KeyArg: EncodeLike<K>, ValArg: EncodeLike<V>>(
        key: KeyArg, 
        val: ValArg
    );

    fn remove<KeyArg: EncodeLike<K>>(key: KeyArg);

    fn mutate<KeyArg: EncodeLike<K>, R, F: FnOnce(&mut Self::Query) -> R>(
        key: KeyArg, 
        f: F
    ) -> R;

    fn try_mutate<KeyArg: EncodeLike<K>, R, E, F: FnOnce(&mut Self::Query) -> Result<R, E>>(
        key: KeyArg, 
        f: F
    ) -> Result<R, E>;

    fn mutate_exists<KeyArg: EncodeLike<K>, R, F: FnOnce(&mut Option<V>) -> R>(
        key: KeyArg, 
        f: F
    ) -> R;

    fn try_mutate_exists<KeyArg: EncodeLike<K>, R, E, F: FnOnce(&mut Option<V>) -> Result<R, E>>(
        key: KeyArg, 
        f: F
    ) -> Result<R, E>;

    fn take<KeyArg: EncodeLike<K>>(key: KeyArg) -> Self::Query;

    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: StorageHasher, KeyArg: EncodeLike<K>>(
        key: KeyArg
    ) -> Option<V>;

    fn decode_len<KeyArg: EncodeLike<K>>(key: KeyArg) -> Option<usize>
    where
        V: StorageDecodeLength,
    { ... }

    fn migrate_key_from_blake<KeyArg: EncodeLike<K>>(key: KeyArg) -> Option<V> { ... }

}
Expand description

A strongly-typed map in storage.

Details on implementation can be found at [generator::StorageMap].

Associated Types

The type that get/take return.

Required methods

Get the storage key used to fetch a value corresponding to a specific key.

Does the value (explicitly) exist in storage?

Load the value associated with the given key from the map.

Try to get the value for the given key from the map.

Returns Ok if it exists, Err if not.

Swap the values of two keys.

Store a value to be associated with the given key from the map.

Remove the value under a key.

Mutate the value under a key.

Mutate the item, only if an Ok value is returned.

Mutate the value under a key.

Deletes the item if mutated to a None.

Mutate the item, only if an Ok value is returned. Deletes the item if mutated to a None.

Take the value under a key.

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.

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

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.

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.

Implementors