Struct flax::Opt

pub struct Opt<F>(_);

Transform a fetch into a optional fetch

Trait Implementations

impl<F: Clone> Clone for Opt<F>

fn clone(&self) -> Opt<F>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<F: Debug> Debug for Opt<F>

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

Formats the value using the given formatter.

impl<'w, F> Fetch<'w> for Opt<F>where
    F: Fetch<'w>,

const MUTABLE: bool = F::MUTABLE

true if the fetch mutates any component and thus needs a change event

const HAS_FILTER: bool = F::HAS_FILTER

true if the fetch has a filter

type Filter = <F as Fetch<'w>>::Filter

The filter associated to the fetch, if applicable. If the fetch does not use a filter, use the crate::All filter

type Prepared = PreparedOpt<<F as Fetch<'w>>::Prepared>

The prepared version of the fetch

fn prepare(&'w self, data: FetchPrepareData<'w>) -> Option<Self::Prepared>

Prepare the query against an archetype. Returns None if doesn’t match. If Self::matches true, this needs to return Some

fn matches(&self, _: FetchPrepareData<'_>) -> bool

Returns true if the fetch matches the archetype

fn describe(&self, f: &mut dyn Write) -> Result

Describes the fetch in a human-readable fashion

fn access(&self, data: FetchPrepareData<'_>) -> Vec<Access>

Returns which components and how will be accessed for an archetype.

fn difference(&self, _: FetchPrepareData<'_>) -> Vec<String>

Returns the required elements in self which are not in archetype

fn filter(&self) -> Self::Filter

Returns the filter if any

impl<'q, F: FetchItem<'q>> FetchItem<'q> for Opt<F>

type Item = Option<<F as FetchItem<'q>>::Item>

The item yielded by the prepared fetch