Struct TrySingle 

pub struct TrySingle<'a, Q>(pub Result<<Q as Query>::Item<'a>, SingleError>)
where
    Q: Query;

Like Single, but contains a Result instead of panicking on error.

This is useful if you need to explicitly handle the situation where the query does not match exactly one entity.

Tuple Fields

0: Result<<Q as Query>::Item<'a>, SingleError>

Methods from Deref<Target = Result<<Q as Query>::Item<'a>, SingleError>>

pub fn is_ok(&self) -> bool

Returns true if the result is Ok.

Examples

let x: Result<i32, &str> = Ok(-3);
assert_eq!(x.is_ok(), true);

let x: Result<i32, &str> = Err("Some error message");
assert_eq!(x.is_ok(), false);

pub fn is_err(&self) -> bool

Returns true if the result is Err.

Examples

let x: Result<i32, &str> = Ok(-3);
assert_eq!(x.is_err(), false);

let x: Result<i32, &str> = Err("Some error message");
assert_eq!(x.is_err(), true);

pub fn as_ref(&self) -> Result<&T, &E>

Converts from &Result<T, E> to Result<&T, &E>.

Produces a new Result, containing a reference into the original, leaving the original in place.

Examples

let x: Result<u32, &str> = Ok(2);
assert_eq!(x.as_ref(), Ok(&2));

let x: Result<u32, &str> = Err("Error");
assert_eq!(x.as_ref(), Err(&"Error"));

pub fn as_mut(&mut self) -> Result<&mut T, &mut E>

Converts from &mut Result<T, E> to Result<&mut T, &mut E>.

Examples

fn mutate(r: &mut Result<i32, i32>) {
    match r.as_mut() {
        Ok(v) => *v = 42,
        Err(e) => *e = 0,
    }
}

let mut x: Result<i32, i32> = Ok(2);
mutate(&mut x);
assert_eq!(x.unwrap(), 42);

let mut x: Result<i32, i32> = Err(13);
mutate(&mut x);
assert_eq!(x.unwrap_err(), 0);

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

where T: Deref,

Converts from Result<T, E> (or &Result<T, E>) to Result<&<T as Deref>::Target, &E>.

Coerces the Ok variant of the original Result via Deref and returns the new Result.

Examples

let x: Result<String, u32> = Ok("hello".to_string());
let y: Result<&str, &u32> = Ok("hello");
assert_eq!(x.as_deref(), y);

let x: Result<String, u32> = Err(42);
let y: Result<&str, &u32> = Err(&42);
assert_eq!(x.as_deref(), y);

pub fn as_deref_mut(&mut self) -> Result<&mut <T as Deref>::Target, &mut E>

where T: DerefMut,

Converts from Result<T, E> (or &mut Result<T, E>) to Result<&mut <T as DerefMut>::Target, &mut E>.

Coerces the Ok variant of the original Result via DerefMut and returns the new Result.

Examples

let mut s = "HELLO".to_string();
let mut x: Result<String, u32> = Ok("hello".to_string());
let y: Result<&mut str, &mut u32> = Ok(&mut s);
assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);

let mut i = 42;
let mut x: Result<String, u32> = Err(42);
let y: Result<&mut str, &mut u32> = Err(&mut i);
assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);

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

Returns an iterator over the possibly contained value.

The iterator yields one value if the result is Result::Ok, otherwise none.

Examples

let x: Result<u32, &str> = Ok(7);
assert_eq!(x.iter().next(), Some(&7));

let x: Result<u32, &str> = Err("nothing!");
assert_eq!(x.iter().next(), None);

pub fn iter_mut(&mut self) -> IterMut<'_, T>

Returns a mutable iterator over the possibly contained value.

The iterator yields one value if the result is Result::Ok, otherwise none.

Examples

let mut x: Result<u32, &str> = Ok(7);
match x.iter_mut().next() {
    Some(v) => *v = 40,
    None => {},
}
assert_eq!(x, Ok(40));

let mut x: Result<u32, &str> = Err("nothing!");
assert_eq!(x.iter_mut().next(), None);

Trait Implementations

impl<'a, Q> Clone for TrySingle<'a, Q>

where Q: Clone + Query, <Q as Query>::Item<'a>: Clone,

fn clone(&self) -> TrySingle<'a, Q>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<'a, Q> Debug for TrySingle<'a, Q>

where Q: Debug + Query, <Q as Query>::Item<'a>: Debug,

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

Formats the value using the given formatter.

impl<'a, Q> Deref for TrySingle<'a, Q>

where Q: Query,

type Target = Result<<Q as Query>::Item<'a>, SingleError>

The resulting type after dereferencing.

fn deref(&self) -> &<TrySingle<'a, Q> as Deref>::Target

Dereferences the value.

impl<'a, Q> DerefMut for TrySingle<'a, Q>

where Q: Query,

fn deref_mut(&mut self) -> &mut <TrySingle<'a, Q> as Deref>::Target

Mutably dereferences the value.

impl<Q> HandlerParam for TrySingle<'_, Q>

where Q: Query + 'static,

type State = FetcherState<Q>

Persistent data stored in the handler.

type This<'a> = TrySingle<'a, Q>

The type produced by this handler param. This must be the type of Self but with the lifetime of 'a.

fn init( world: &mut World, config: &mut HandlerConfig, ) -> Result<<TrySingle<'_, Q> as HandlerParam>::State, InitError>

Initializes the handler using the input World and HandlerConfig.

unsafe fn get<'a>( state: &'a mut <TrySingle<'_, Q> as HandlerParam>::State, _info: &'a HandlerInfo, _event_ptr: EventPtr<'a>, _target_location: EntityLocation, world: UnsafeWorldCell<'a>, ) -> <TrySingle<'_, Q> as HandlerParam>::This<'a>

Obtains a new instance of the handler parameter.

fn refresh_archetype( state: &mut <TrySingle<'_, Q> as HandlerParam>::State, arch: &Archetype, )

Refresh an archetype for this handler param. Called whenever Handler::refresh_archetype is called.

fn remove_archetype( state: &mut <TrySingle<'_, Q> as HandlerParam>::State, arch: &Archetype, )

Remove the given archetype for this handler param. Called whenever Handler::remove_archetype is called.

impl<'a, Q> Ord for TrySingle<'a, Q>

where Q: Ord + Query, <Q as Query>::Item<'a>: Ord,

fn cmp(&self, other: &TrySingle<'a, Q>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<'a, Q> PartialEq for TrySingle<'a, Q>

where Q: PartialEq + Query, <Q as Query>::Item<'a>: PartialEq,

fn eq(&self, other: &TrySingle<'a, Q>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a, Q> PartialOrd for TrySingle<'a, Q>

where Q: PartialOrd + Query, <Q as Query>::Item<'a>: PartialOrd,

fn partial_cmp(&self, other: &TrySingle<'a, Q>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, Q> Copy for TrySingle<'a, Q>

where Q: Copy + Query, <Q as Query>::Item<'a>: Copy,

impl<'a, Q> Eq for TrySingle<'a, Q>

where Q: Eq + Query, <Q as Query>::Item<'a>: Eq,

impl<'a, Q> StructuralPartialEq for TrySingle<'a, Q>

where Q: Query,