Struct frame_support::pallet_prelude::StorageNMap

pub struct StorageNMap<Prefix, Key, Value, QueryKind = OptionQuery, OnEmpty = GetDefault, MaxValues = GetDefault>(_);

A type that allow to store values for an arbitrary number of keys in the form of (Key<Hasher1, key1>, Key<Hasher2, key2>, ..., Key<HasherN, keyN>).

Each value is stored at:

Twox128(Prefix::pallet_prefix())
		++ Twox128(Prefix::STORAGE_PREFIX)
		++ Hasher1(encode(key1))
		++ Hasher2(encode(key2))
	++ ...
	++ HasherN(encode(keyN))

Warning

If the keys are not trusted (e.g. can be set by a user), a cryptographic hasher such as blake2_128_concat must be used for the key hashers. Otherwise, other values in storage can be compromised.

Implementations

impl<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> StorageNMap<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> where
    Prefix: StorageInstance,
    Key: KeyGenerator,
    Value: FullCodec,
    QueryKind: QueryKindTrait<Value, OnEmpty>,
    OnEmpty: Get<QueryKind::Query> + 'static,
    MaxValues: Get<Option<u32>>, 

pub fn hashed_key_for<KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter>(
    key: KArg
) -> Vec<u8>

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

pub fn contains_key<KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter>(
    key: KArg
) -> bool

Does the value (explicitly) exist in storage?

pub fn get<KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter>(
    key: KArg
) -> QueryKind::Query

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

pub fn try_get<KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter>(
    key: KArg
) -> Result<Value, ()>

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

Returns Ok if it exists, Err if not.

pub fn take<KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter>(
    key: KArg
) -> QueryKind::Query

Take a value from storage, removing it afterwards.

pub fn swap<KOther, KArg1, KArg2>(key1: KArg1, key2: KArg2) where
    KOther: KeyGenerator,
    KArg1: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter,
    KArg2: EncodeLikeTuple<KOther::KArg> + TupleToEncodedIter, 

Swap the values of two key-pairs.

pub fn insert<KArg, VArg>(key: KArg, val: VArg) where
    KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter,
    VArg: EncodeLike<Value>, 

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

pub fn remove<KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter>(key: KArg)

Remove the value under the given keys.

pub fn remove_prefix<KP>(
    partial_key: KP,
    limit: Option<u32>
) -> KillStorageResult where
    Key: HasKeyPrefix<KP>, 

Remove all values under the first key.

pub fn iter_prefix_values<KP>(partial_key: KP) -> PrefixIterator<Value> where
    Key: HasKeyPrefix<KP>, 

Iterate over values that share the first key.

pub fn mutate<KArg, R, F>(key: KArg, f: F) -> R where
    KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter,
    F: FnOnce(&mut QueryKind::Query) -> R, 

Mutate the value under the given keys.

pub fn try_mutate<KArg, R, E, F>(key: KArg, f: F) -> Result<R, E> where
    KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter,
    F: FnOnce(&mut QueryKind::Query) -> Result<R, E>, 

Mutate the value under the given keys when the closure returns Ok.

pub fn mutate_exists<KArg, R, F>(key: KArg, f: F) -> R where
    KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter,
    F: FnOnce(&mut Option<Value>) -> R, 

Mutate the value under the given keys. Deletes the item if mutated to a None.

pub fn try_mutate_exists<KArg, R, E, F>(key: KArg, f: F) -> Result<R, E> where
    KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter,
    F: FnOnce(&mut Option<Value>) -> Result<R, E>, 

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

pub fn append<Item, EncodeLikeItem, KArg>(key: KArg, item: EncodeLikeItem) where
    KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter,
    Item: Encode,
    EncodeLikeItem: EncodeLike<Item>,
    Value: StorageAppend<Item>, 

Append the given item to the value in the storage.

Value is required to implement StorageAppend.

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.

pub fn decode_len<KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter>(
    key: KArg
) -> Option<usize> where
    Value: StorageDecodeLength, 

Read the length of the storage value without decoding the entire value under the given key1 and key2.

Value 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.

pub fn migrate_keys<KArg>(key: KArg, hash_fns: Key::HArg) -> Option<Value> where
    KArg: EncodeLikeTuple<Key::KArg> + TupleToEncodedIter, 

Migrate an item with the given key from defunct hash_fns to the current hashers.

If the key doesn’t exist, then it’s a no-op. If it does, then it returns its value.

pub fn remove_all(limit: Option<u32>) -> KillStorageResult

Remove all value of the storage.

pub fn iter_values() -> PrefixIterator<Value>

Iter over all value of the storage.

NOTE: If a value failed to decode because storage is corrupted then it is skipped.

pub fn translate_values<OldValue: Decode, F: FnMut(OldValue) -> Option<Value>>(
    f: F
)

Translate the values of all elements by a function f, in the map in no particular order. By returning None from f for an element, you’ll remove it from the map.

NOTE: If a value fail to decode because storage is corrupted then it is skipped.

Warning

This function must be used with care, before being updated the storage still contains the old type, thus other calls (such as get) will fail at decoding it.

Usage

This would typically be called inside the module implementation of on_runtime_upgrade.

impl<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> StorageNMap<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> where
    Prefix: StorageInstance,
    Key: ReversibleKeyGenerator,
    Value: FullCodec,
    QueryKind: QueryKindTrait<Value, OnEmpty>,
    OnEmpty: Get<QueryKind::Query> + 'static,
    MaxValues: Get<Option<u32>>, 

pub fn iter_prefix<KP>(
    kp: KP
) -> PrefixIterator<(<Key as HasKeyPrefix<KP>>::Suffix, Value)> where
    Key: HasReversibleKeyPrefix<KP>, 

Enumerate all elements in the map with prefix key kp in no particular order.

If you add or remove values whose prefix key is kp to the map while doing this, you’ll get undefined results.

pub fn iter_prefix_from<KP>(
    kp: KP,
    starting_raw_key: Vec<u8>
) -> PrefixIterator<(<Key as HasKeyPrefix<KP>>::Suffix, Value)> where
    Key: HasReversibleKeyPrefix<KP>, 

Enumerate all elements in the map with prefix key kp after a specified starting_raw_key in no particular order.

If you add or remove values whose prefix key is kp to the map while doing this, you’ll get undefined results.

pub fn iter_key_prefix<KP>(
    kp: KP
) -> KeyPrefixIterator<<Key as HasKeyPrefix<KP>>::Suffix> where
    Key: HasReversibleKeyPrefix<KP>, 

Enumerate all suffix keys in the map with prefix key kp in no particular order.

If you add or remove values whose prefix key is kp to the map while doing this, you’ll get undefined results.

pub fn iter_key_prefix_from<KP>(
    kp: KP,
    starting_raw_key: Vec<u8>
) -> KeyPrefixIterator<<Key as HasKeyPrefix<KP>>::Suffix> where
    Key: HasReversibleKeyPrefix<KP>, 

Enumerate all suffix keys in the map with prefix key kp after a specified starting_raw_key in no particular order.

If you add or remove values whose prefix key is kp to the map while doing this, you’ll get undefined results.

pub fn drain_prefix<KP>(
    kp: KP
) -> PrefixIterator<(<Key as HasKeyPrefix<KP>>::Suffix, Value)> where
    Key: HasReversibleKeyPrefix<KP>, 

Remove all elements from the map with prefix key kp and iterate through them in no particular order.

If you add elements with prefix key k1 to the map while doing this, you’ll get undefined results.

pub fn iter() -> PrefixIterator<(Key::Key, Value)>

Enumerate all elements in the map in no particular order.

If you add or remove values to the map while doing this, you’ll get undefined results.

pub fn iter_from(starting_raw_key: Vec<u8>) -> PrefixIterator<(Key::Key, Value)>

Enumerate all elements in the map after a specified starting_key in no particular order.

If you add or remove values to the map while doing this, you’ll get undefined results.

pub fn iter_keys() -> KeyPrefixIterator<Key::Key>

Enumerate all keys in the map in no particular order.

If you add or remove values to the map while doing this, you’ll get undefined results.

pub fn iter_keys_from(starting_raw_key: Vec<u8>) -> KeyPrefixIterator<Key::Key>

Enumerate all keys in the map after a specified starting_raw_key in no particular order.

If you add or remove values to the map while doing this, you’ll get undefined results.

pub fn drain() -> PrefixIterator<(Key::Key, Value)>

Remove all elements from the map and iterate through them in no particular order.

If you add elements to the map while doing this, you’ll get undefined results.

pub fn translate<O: Decode, F: FnMut(Key::Key, O) -> Option<Value>>(f: F)

Translate the values of all elements by a function f, in the map in no particular order.

By returning None from f for an element, you’ll remove it from the map.

NOTE: If a value fail to decode because storage is corrupted then it is skipped.

Trait Implementations

impl<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> PartialStorageInfoTrait for StorageNMap<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> where
    Prefix: StorageInstance,
    Key: KeyGenerator,
    Value: FullCodec,
    QueryKind: QueryKindTrait<Value, OnEmpty>,
    OnEmpty: Get<QueryKind::Query> + 'static,
    MaxValues: Get<Option<u32>>, 

It doesn’t require to implement MaxEncodedLen and give no information for max_size.

fn partial_storage_info() -> Vec<StorageInfo>

impl<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> StorageEntryMetadataBuilder for StorageNMap<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> where
    Prefix: StorageInstance,
    Key: KeyGenerator,
    Value: FullCodec + StaticTypeInfo,
    QueryKind: QueryKindTrait<Value, OnEmpty>,
    OnEmpty: Get<QueryKind::Query> + 'static,
    MaxValues: Get<Option<u32>>, 

fn build_metadata(
    docs: Vec<&'static str>,
    entries: &mut Vec<StorageEntryMetadata>
)

Build into entries the storage metadata entries of a storage given some docs.

impl<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> StorageInfoTrait for StorageNMap<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> where
    Prefix: StorageInstance,
    Key: KeyGenerator + KeyGeneratorMaxEncodedLen,
    Value: FullCodec + MaxEncodedLen,
    QueryKind: QueryKindTrait<Value, OnEmpty>,
    OnEmpty: Get<QueryKind::Query> + 'static,
    MaxValues: Get<Option<u32>>, 

fn storage_info() -> Vec<StorageInfo>

impl<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> StoragePrefixedMap<Value> for StorageNMap<Prefix, Key, Value, QueryKind, OnEmpty, MaxValues> where
    Prefix: StorageInstance,
    Key: KeyGenerator,
    Value: FullCodec,
    QueryKind: QueryKindTrait<Value, OnEmpty>,
    OnEmpty: Get<QueryKind::Query> + 'static,
    MaxValues: Get<Option<u32>>, 

fn module_prefix() -> &'static [u8]

Module prefix. Used for generating final key.

fn storage_prefix() -> &'static [u8]

Storage prefix. Used for generating final key.

fn final_prefix() -> [u8; 32]

Final full prefix that prefixes all keys.

fn remove_all(limit: Option<u32>) -> KillStorageResult

Remove all value of the storage.

fn iter_values() -> PrefixIterator<Value>

Iter over all value of the storage.

fn translate_values<OldValue: Decode, F: FnMut(OldValue) -> Option<Value>>(f: F)

Translate the values of all elements by a function f, in the map in no particular order. By returning None from f for an element, you’ll remove it from the map.