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

pub trait StorageDoubleMap<K1: FullEncode, K2: FullEncode, V: FullCodec> {
    type Query;

Show methods    fn hashed_key_for<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Vec<u8>ⓘ
Notable traits for Vec<u8, A>
impl<A> Write for Vec<u8, A> where
    A: Allocator, 

    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 try_get<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Result<V, ()>
    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, 
        limit: Option<u32>
    ) -> KillStorageResult
    where
        KArg1: EncodeLike<K1>;

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

    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 mutate_exists<KArg1, KArg2, R, F>(k1: KArg1, k2: KArg2, f: F) -> R
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>,
        F: FnOnce(&mut Option<V>) -> R;

    fn try_mutate_exists<KArg1, KArg2, R, E, F>(
        k1: KArg1, 
        k2: KArg2, 
        f: F
    ) -> Result<R, E>
    where
        KArg1: EncodeLike<K1>,
        KArg2: EncodeLike<K2>,
        F: FnOnce(&mut Option<V>) -> 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,
    { ... }

}
Expand description

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

The type that get/take returns.

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 double map.

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

Returns Ok if it exists, Err if not.

Take a value from storage, removing it afterwards.

Swap the values of two key-pairs.

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

Remove the value under the given keys.

Remove all values under the first key.

Iterate over values that share the first key.

Mutate the value under the given keys.

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

Mutate the value under the given keys. 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.

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.

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.

Provided methods

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.

Implementors