Struct KeyedSlot 

pub struct KeyedSlot<Parent, Child, K> {
    pub read: for<'a> fn(&'a Parent, &K) -> Option<&'a Child>,
    pub write: fn(Option<&Parent>, &K, Child) -> Parent,
}

Where one of a family of children keeps its record, inside its parent’s.

Slot names a fixed place, which is right when a parent has one child of a kind. A parent holding a family — one instance per round, per epoch, per slot of a log — needs a place per member, and the member is not known when the slot is written.

The key is data, not a capture. read and write stay fn pointers and take the key as an argument, so a keyed slot still names one fixed function; what varies is what it is applied to. That is what Slot’s own note means by “a slot must not capture”: a slot closing over state would be a different function on different calls, and this is the same function every time.

The parent is responsible for the keyspace being a keyspace. Two children handed the same key share a record, exactly as two Slots naming one field would.

Fields

read: for<'a> fn(&'a Parent, &K) -> Option<&'a Child>

The child’s record for key, as it sits inside the parent’s.

write: fn(Option<&Parent>, &K, Child) -> Parent

The parent’s record with the child’s part for key replaced.

Trait Implementations

impl<Parent, Child, K> Clone for KeyedSlot<Parent, Child, K>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<Parent, Child, K> Copy for KeyedSlot<Parent, Child, K>

impl<Parent, Child, K> Debug for KeyedSlot<Parent, Child, K>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.