Trait frame_support::storage::types::QueryKindTrait

pub trait QueryKindTrait<Value, OnEmpty> {
    type Query: FullCodec + 'static;

    const METADATA: StorageEntryModifier;

    fn from_optional_value_to_query(v: Option<Value>) -> Self::Query;
    fn from_query_to_optional_value(v: Self::Query) -> Option<Value>;
}

Trait implementing how the storage optional value is converted into the queried type.

It is implemented by:

• OptionQuery which converts an optional value to an optional value, used when querying storage returns an optional value.
• ResultQuery which converts an optional value to a result value, used when querying storage returns a result value.
• ValueQuery which converts an optional value to a value, used when querying storage returns a value.

Required Associated Types

type Query: FullCodec + 'static

Type returned on query

Required Associated Constants

const METADATA: StorageEntryModifier

Metadata for the storage kind.

Required Methods

fn from_optional_value_to_query(v: Option<Value>) -> Self::Query

Convert an optional value (i.e. some if trie contains the value or none otherwise) to the query.

fn from_query_to_optional_value(v: Self::Query) -> Option<Value>

Convert a query to an optional value.

Implementors

impl<Value> QueryKindTrait<Value, GetDefault> for OptionQuerywhere
    Value: FullCodec + 'static,

const METADATA: StorageEntryModifier = StorageEntryModifier::Optional

type Query = Option<Value>

impl<Value, Error, OnEmpty> QueryKindTrait<Value, OnEmpty> for ResultQuery<Error>where
    Value: FullCodec + 'static,
    Error: FullCodec + 'static,
    OnEmpty: Get<Result<Value, Error>>,

const METADATA: StorageEntryModifier = StorageEntryModifier::Optional

type Query = Result<Value, Error>

impl<Value, OnEmpty> QueryKindTrait<Value, OnEmpty> for ValueQuerywhere
    Value: FullCodec + 'static,
    OnEmpty: Get<Value>,

const METADATA: StorageEntryModifier = StorageEntryModifier::Default

type Query = Value