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

pub trait StorageMap<K: FullEncode, V: FullCodec> {
    type Query;
    fn hashed_key_for<KeyArg: EncodeLike<K>>(key: KeyArg) -> Vec<u8>;

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

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

    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<Items, Item, EncodeLikeItem, KeyArg>(
        key: KeyArg, 
        items: Items
    ) -> Result<(), &'static str>
    where
        KeyArg: EncodeLike<K>,
        Item: Encode,
        EncodeLikeItem: EncodeLike<Item>,
        V: EncodeAppend<Item = Item>,
        Items: IntoIterator<Item = EncodeLikeItem>,
        Items::IntoIter: ExactSizeIterator;

    fn append_or_insert<Items, Item, EncodeLikeItem, KeyArg>(
        key: KeyArg, 
        items: Items
    )
    where
        KeyArg: EncodeLike<K>,
        Item: Encode,
        EncodeLikeItem: EncodeLike<Item>,
        V: EncodeAppend<Item = Item>,
        Items: IntoIterator<Item = EncodeLikeItem> + Clone + EncodeLike<V>,
        Items::IntoIter: ExactSizeIterator;

    fn decode_len<KeyArg: EncodeLike<K>>(
        key: KeyArg
    ) -> Result<usize, &'static str>
    where
        V: DecodeLength + Len;
}

A strongly-typed map in storage.

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

Associated Types

type Query

The type that get/take return.

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Required methods

ⓘImportant traits for Vec<u8>
fn hashed_key_for<KeyArg: EncodeLike<K>>(key: KeyArg) -> Vec<u8>

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

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

Does the value (explicitly) exist in storage?

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

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

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

Swap the values of two keys.

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

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

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

Remove the value under a key.

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

Mutate the value under a key.

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

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

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

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

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

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

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

Take the value under a key.

fn append<Items, Item, EncodeLikeItem, KeyArg>(
    key: KeyArg,
    items: Items
) -> Result<(), &'static str> where
    KeyArg: EncodeLike<K>,
    Item: Encode,
    EncodeLikeItem: EncodeLike<Item>,
    V: EncodeAppend<Item = Item>,
    Items: IntoIterator<Item = EncodeLikeItem>,
    Items::IntoIter: ExactSizeIterator, 

Append the given items to the value in the storage.

V is required to implement codec::EncodeAppend.

fn append_or_insert<Items, Item, EncodeLikeItem, KeyArg>(
    key: KeyArg,
    items: Items
) where
    KeyArg: EncodeLike<K>,
    Item: Encode,
    EncodeLikeItem: EncodeLike<Item>,
    V: EncodeAppend<Item = Item>,
    Items: IntoIterator<Item = EncodeLikeItem> + Clone + EncodeLike<V>,
    Items::IntoIter: ExactSizeIterator, 

Safely append the given items to the value in the storage. If a codec error occurs, then the old (presumably corrupt) value is replaced with the given items.

V is required to implement codec::EncodeAppend.

fn decode_len<KeyArg: EncodeLike<K>>(key: KeyArg) -> Result<usize, &'static str> where
    V: DecodeLength + Len, 

Read the length of the value in a fast way, without decoding the entire value.

T is required to implement Codec::DecodeLength.

Note that 0 is returned as the default value if no encoded value exists at the given key. Therefore, this function cannot be used as a sign of existence. use the ::contains_key() function for this purpose.

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Implementors

impl<K: FullEncode, V: FullCodec, G: StorageMap<K, V>> StorageMap<K, V> for G[src]

type Query = G::Query

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