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

pub trait StorageDoubleMap<K1: FullEncode, K2: FullEncode, V: FullCodec> {
    type Query;
    fn hashed_key_for<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Vec<u8>ⓘ
Notable traits for Vec<u8>
impl Write for Vec<u8>

    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>;

    fn contains_key<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> bool
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>;

    fn get<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Self::Query
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>;

    fn take<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Self::Query
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>;

    fn swap<XKArg1, XKArg2, YKArg1, YKArg2>(
        x_k1: XKArg1, 
        x_k2: XKArg2, 
        y_k1: YKArg1, 
        y_k2: YKArg2
    )
    where
        XKArg1: EncodeLike<K1>,
        XKArg2: EncodeLike<K2>,
        YKArg1: EncodeLike<K1>,
        YKArg2: EncodeLike<K2>;

    fn insert<KArg1, KArg2, VArg>(k1: KArg1, k2: KArg2, val: VArg)
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>,
        VArg: EncodeLike<V>;

    fn remove<KArg1, KArg2>(k1: KArg1, k2: KArg2)
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>;

    fn remove_prefix<KArg1: ?Sized>(k1: KArg1)
    where
        KArg1: EncodeLike<K1>;

    fn iter_prefix_values<KArg1: ?Sized>(k1: KArg1) -> PrefixIterator<V>ⓘ
Notable traits for PrefixIterator<Value>
impl<Value: Decode> Iterator for PrefixIterator<Value>    type Item = Value;

    where
        KArg1: EncodeLike<K1>;

    fn mutate<KArg1, KArg2, R, F>(k1: KArg1, k2: KArg2, f: F) -> R
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>,
        F: FnOnce(&mut Self::Query) -> R;

    fn try_mutate<KArg1, KArg2, R, E, F>(
        k1: KArg1, 
        k2: KArg2, 
        f: F
    ) -> Result<R, E>
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>,
        F: FnOnce(&mut Self::Query) -> Result<R, E>;

    fn append<Item, EncodeLikeItem, KArg1, KArg2>(
        k1: KArg1, 
        k2: KArg2, 
        item: EncodeLikeItem
    )
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>,
        Item: Encode,
        EncodeLikeItem: EncodeLike<Item>,
        V: StorageAppend<Item>;

    fn migrate_keys<OldHasher1: StorageHasher, OldHasher2: StorageHasher, KeyArg1: EncodeLike<K1>, KeyArg2: EncodeLike<K2>>(
        key1: KeyArg1, 
        key2: KeyArg2
    ) -> Option<V>;

    fn decode_len<KArg1, KArg2>(key1: KArg1, key2: KArg2) -> Option<usize>
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>,
        V: StorageDecodeLength,
    { ... }
}

An implementation of a map with a two keys.

It provides an important ability to efficiently remove all entries that have a common first key.

Details on implementation can be found at [generator::StorageDoubleMap]

Associated Types

type Query

The type that get/take returns.

Loading content...

Required methods

fn hashed_key_for<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Vec<u8>ⓘ

Notable traits for Vec<u8>

impl Write for Vec<u8>
 where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>, 

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

fn contains_key<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> bool where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>, 

Does the value (explicitly) exist in storage?

fn get<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Self::Query where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>, 

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

fn take<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Self::Query where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>, 

Take a value from storage, removing it afterwards.

fn swap<XKArg1, XKArg2, YKArg1, YKArg2>(
    x_k1: XKArg1,
    x_k2: XKArg2,
    y_k1: YKArg1,
    y_k2: YKArg2
) where
    XKArg1: EncodeLike<K1>,
    XKArg2: EncodeLike<K2>,
    YKArg1: EncodeLike<K1>,
    YKArg2: EncodeLike<K2>, 

Swap the values of two key-pairs.

fn insert<KArg1, KArg2, VArg>(k1: KArg1, k2: KArg2, val: VArg) where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>,
    VArg: EncodeLike<V>, 

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

fn remove<KArg1, KArg2>(k1: KArg1, k2: KArg2) where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>, 

Remove the value under the given keys.

fn remove_prefix<KArg1: ?Sized>(k1: KArg1) where
    KArg1: EncodeLike<K1>, 

Remove all values under the first key.

fn iter_prefix_values<KArg1: ?Sized>(k1: KArg1) -> PrefixIterator<V>ⓘ

Notable traits for PrefixIterator<Value>

impl<Value: Decode> Iterator for PrefixIterator<Value> type Item = Value;
 where
    KArg1: EncodeLike<K1>, 

Iterate over values that share the first key.

fn mutate<KArg1, KArg2, R, F>(k1: KArg1, k2: KArg2, f: F) -> R where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>,
    F: FnOnce(&mut Self::Query) -> R, 

Mutate the value under the given keys.

fn try_mutate<KArg1, KArg2, R, E, F>(k1: KArg1, k2: KArg2, f: F) -> Result<R, E> where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>,
    F: FnOnce(&mut Self::Query) -> Result<R, E>, 

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

fn append<Item, EncodeLikeItem, KArg1, KArg2>(
    k1: KArg1,
    k2: KArg2,
    item: EncodeLikeItem
) where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>,
    Item: Encode,
    EncodeLikeItem: EncodeLike<Item>,
    V: StorageAppend<Item>, 

Append the given item to the value in the storage.

V 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.

fn migrate_keys<OldHasher1: StorageHasher, OldHasher2: StorageHasher, KeyArg1: EncodeLike<K1>, KeyArg2: EncodeLike<K2>>(
    key1: KeyArg1,
    key2: KeyArg2
) -> Option<V>

Migrate an item with the given key1 and key2 from defunct OldHasher1 and OldHasher2 to the current hashers.

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

Loading content...

Provided methods

fn decode_len<KArg1, KArg2>(key1: KArg1, key2: KArg2) -> Option<usize> where
    KArg1: EncodeLike<K1>,
    KArg2: EncodeLike<K2>,
    V: StorageDecodeLength, 

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

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.

Loading content...

Implementors

impl<K1, K2, V, G> StorageDoubleMap<K1, K2, V> for G where
    K1: FullEncode,
    K2: FullEncode,
    V: FullCodec,
    G: StorageDoubleMap<K1, K2, V>, [src]

type Query = G::Query

Loading content...