Trait frame_election_provider_support::SortedListProvider

pub trait SortedListProvider<AccountId> {
    type Error;
    fn iter() -> Box<dyn Iterator<Item = AccountId>>;
    fn count() -> u32;
    fn contains(id: &AccountId) -> bool;
    fn on_insert(id: AccountId, weight: VoteWeight) -> Result<(), Self::Error>;
    fn on_update(id: &AccountId, weight: VoteWeight);
    fn on_remove(id: &AccountId);
    fn unsafe_regenerate(
        all: impl IntoIterator<Item = AccountId>, 
        weight_of: Box<dyn Fn(&AccountId) -> VoteWeight>
    ) -> u32;
    fn unsafe_clear();
    fn sanity_check() -> Result<(), &'static str>;

    fn weight_update_worst_case(
        _who: &AccountId, 
        _is_increase: bool
    ) -> VoteWeight { ... }
}

A utility trait for something to implement ElectionDataProvider in a sensible way.

This is generic over AccountId and it can represent a validator, a nominator, or any other entity.

To simplify the trait, the VoteWeight is hardcoded as the weight of each entity. The weights are ascending, the higher, the better. In the long term, if this trait ends up having use cases outside of the election context, it is easy enough to make it generic over the VoteWeight.

Something that implements this trait will do a best-effort sort over ids, and thus can be used on the implementing side of ElectionDataProvider.

Associated Types

type Error

The list’s error type.

Required methods

fn iter() -> Box<dyn Iterator<Item = AccountId>>

An iterator over the list, which can have take called on it.

fn count() -> u32

The current count of ids in the list.

fn contains(id: &AccountId) -> bool

Return true if the list already contains id.

fn on_insert(id: AccountId, weight: VoteWeight) -> Result<(), Self::Error>

Hook for inserting a new id.

fn on_update(id: &AccountId, weight: VoteWeight)

Hook for updating a single id.

fn on_remove(id: &AccountId)

Hook for removing am id from the list.

fn unsafe_regenerate(
    all: impl IntoIterator<Item = AccountId>,
    weight_of: Box<dyn Fn(&AccountId) -> VoteWeight>
) -> u32

Regenerate this list from scratch. Returns the count of items inserted.

This should typically only be used at a runtime upgrade.

WARNING

This function should be called with care, regenerate will remove the current list write the new list, which can lead to too many storage accesses, exhausting the block weight.

fn unsafe_clear()

Remove all items from the list.

WARNING

This function should never be called in production settings because it can lead to an unbounded amount of storage accesses.

fn sanity_check() -> Result<(), &'static str>

Sanity check internal state of list. Only meant for debug compilation.

Provided methods

fn weight_update_worst_case(_who: &AccountId, _is_increase: bool) -> VoteWeight

If who changes by the returned amount they are guaranteed to have a worst case change in their list position.

Implementors