Struct hecs_schedule::borrow::MaybeRead

#[repr(transparent)]
pub struct MaybeRead<'a, T>(_);

Wrapper type for an immutably borrowed value from schedule context which may not exist.

Implementations

impl<'a, T> MaybeRead<'a, T>

pub fn new(borrow: Option<AtomicRef<'a, T>>) -> Self

Creates a new MaybeRead borrow from an atomic ref

pub fn option(&self) -> Option<&AtomicRef<'a, T>>

Returns the containing option suitable for match expressions

Methods from Deref<Target = Option<AtomicRef<'a, T>>>

pub fn is_some(&self) -> bool

Returns true if the option is a Some value.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_some(), true);

let x: Option<u32> = None;
assert_eq!(x.is_some(), false);

pub fn is_none(&self) -> bool

Returns true if the option is a None value.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_none(), false);

let x: Option<u32> = None;
assert_eq!(x.is_none(), true);

pub fn contains<U>(&self, x: &U) -> bool where
    U: PartialEq<T>, 

🔬 This is a nightly-only experimental API. (option_result_contains)

Returns true if the option is a Some value containing the given value.

Examples

#![feature(option_result_contains)]

let x: Option<u32> = Some(2);
assert_eq!(x.contains(&2), true);

let x: Option<u32> = Some(3);
assert_eq!(x.contains(&2), false);

let x: Option<u32> = None;
assert_eq!(x.contains(&2), false);

pub fn as_ref(&self) -> Option<&T>

Converts from &Option<T> to Option<&T>.

Examples

Converts an Option<String> into an Option<usize>, preserving the original. The map method takes the self argument by value, consuming the original, so this technique uses as_ref to first take an Option to a reference to the value inside the original.

let text: Option<String> = Some("Hello, world!".to_string());
// First, cast `Option<String>` to `Option<&String>` with `as_ref`,
// then consume *that* with `map`, leaving `text` on the stack.
let text_length: Option<usize> = text.as_ref().map(|s| s.len());
println!("still can print text: {:?}", text);

pub fn as_pin_ref(self: Pin<&Option<T>>) -> Option<Pin<&T>>

Converts from Pin<&Option<T>> to Option<Pin<&T>>.

pub fn as_pin_mut(self: Pin<&mut Option<T>>) -> Option<Pin<&mut T>>

Converts from Pin<&mut Option<T>> to Option<Pin<&mut T>>.

pub fn iter(&self) -> Iter<'_, T>

Returns an iterator over the possibly contained value.

Examples

let x = Some(4);
assert_eq!(x.iter().next(), Some(&4));

let x: Option<u32> = None;
assert_eq!(x.iter().next(), None);

pub fn as_deref(&self) -> Option<&<T as Deref>::Target> where
    T: Deref, 

Converts from Option<T> (or &Option<T>) to Option<&T::Target>.

Leaves the original Option in-place, creating a new one with a reference to the original one, additionally coercing the contents via Deref.

Examples

let x: Option<String> = Some("hey".to_owned());
assert_eq!(x.as_deref(), Some("hey"));

let x: Option<String> = None;
assert_eq!(x.as_deref(), None);

Trait Implementations

impl<'a, T> Clone for MaybeRead<'a, T>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'a, T: 'static> ComponentBorrow for MaybeRead<'a, T>

fn borrows() -> Borrows

Returns a list of all component accesses

fn has<U: IntoAccess>() -> bool

Returns true if U exists in Self

fn has_dynamic(id: TypeId, exclusive: bool) -> bool

Returns true if id exists in Self

impl<'a, T: 'static> ContextBorrow<'a> for MaybeRead<'a, T>

type Target = Self

The resulting type after borrowing from context

fn borrow(context: &'a Context<'_>) -> Result<Self::Target>

Borrow type from context

impl<'a, T: Debug> Debug for MaybeRead<'a, T>

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

Formats the value using the given formatter.

impl<'a, T> Deref for MaybeRead<'a, T>

type Target = Option<AtomicRef<'a, T>>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T: Component> IntoBorrow for MaybeRead<'_, T>

type Borrow = MaybeBorrower<T>

The borrow type