Struct frame_support::pallet_prelude::NMapKey

pub struct NMapKey<Hasher, KeyType>(_);

A type used exclusively by storage maps as their key type.

The final key generated has the following form:

Hasher1(encode(key1))
    ++ Hasher2(encode(key2))
    ++ ...
    ++ HasherN(encode(keyN))

Trait Implementations

impl<H: StorageHasher, K: FullCodec> KeyGenerator for Key<H, K>

type Key = K

type KArg = (K,)

type HashFn = Box<dyn FnOnce(&[u8]) -> Vec<u8>>

type HArg = (Self::HashFn,)

const HASHER_METADATA: &'static [StorageHasher]

fn final_key<KArg: EncodeLikeTuple<Self::KArg> + TupleToEncodedIter>(
    key: KArg
) -> Vec<u8>

Given a key tuple, calculate the final key by encoding each element individuallly and hashing them using the corresponding hasher in the KeyGenerator.

fn migrate_key<KArg: EncodeLikeTuple<Self::KArg> + TupleToEncodedIter>(
    key: &KArg,
    hash_fns: Self::HArg
) -> Vec<u8>

Given a key tuple, migrate the keys from using the old hashers as given by hash_fns to using the newer hashers as specified by this KeyGenerator.

impl<H: StorageHasher, K: FullCodec + MaxEncodedLen> KeyGeneratorMaxEncodedLen for Key<H, K>

fn key_max_encoded_len() -> usize

impl<H: ReversibleStorageHasher, K: FullCodec> ReversibleKeyGenerator for Key<H, K>

type ReversibleHasher = H

fn decode_final_key(key_material: &[u8]) -> Result<(Self::Key, &[u8]), Error>