[−][src]Struct vec_option::OptionProxy
A proxy to a mutable reference to an option in a VecOption<T>
If this OptionProxy
is leaked, then the option in the VecOption<T>
will be set to None
and the old value of that element will be leaked
This serves as a way to access the option directly, and will update the VecOption<T>
on drop
Methods from Deref<Target = Option<T>>
#[must_use = "if you intended to assert that this has a value, consider `.unwrap()` instead"]
pub fn is_some(&self) -> bool
1.0.0[src]
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);
#[must_use = "if you intended to assert that this doesn\'t have a value, consider `.and_then(|| panic!(\"`Option` had a value when expected `None`\"))` instead"]
pub fn is_none(&self) -> bool
1.0.0[src]
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);
#[must_use]
pub fn contains<U>(&self, x: &U) -> bool where
U: PartialEq<T>,
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U: PartialEq<T>,
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>
1.0.0[src]
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_mut(&mut self) -> Option<&mut T>
1.0.0[src]
Converts from &mut Option<T>
to Option<&mut T>
.
Examples
let mut x = Some(2); match x.as_mut() { Some(v) => *v = 42, None => {}, } assert_eq!(x, Some(42));
pub fn as_pin_ref(self: Pin<&'a Option<T>>) -> Option<Pin<&'a T>>
1.33.0[src]
pub fn as_pin_mut(self: Pin<&'a mut Option<T>>) -> Option<Pin<&'a mut T>>
1.33.0[src]
pub fn iter(&self) -> Iter<T>
1.0.0[src]
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 iter_mut(&mut self) -> IterMut<T>
1.0.0[src]
Returns a mutable iterator over the possibly contained value.
Examples
let mut x = Some(4); match x.iter_mut().next() { Some(v) => *v = 42, None => {}, } assert_eq!(x, Some(42)); let mut x: Option<u32> = None; assert_eq!(x.iter_mut().next(), None);
pub fn get_or_insert(&mut self, v: T) -> &mut T
1.20.0[src]
Inserts v
into the option if it is None
, then
returns a mutable reference to the contained value.
Examples
let mut x = None; { let y: &mut u32 = x.get_or_insert(5); assert_eq!(y, &5); *y = 7; } assert_eq!(x, Some(7));
pub fn get_or_insert_with<F>(&mut self, f: F) -> &mut T where
F: FnOnce() -> T,
1.20.0[src]
F: FnOnce() -> T,
Inserts a value computed from f
into the option if it is None
, then
returns a mutable reference to the contained value.
Examples
let mut x = None; { let y: &mut u32 = x.get_or_insert_with(|| 5); assert_eq!(y, &5); *y = 7; } assert_eq!(x, Some(7));
pub fn take(&mut self) -> Option<T>
1.0.0[src]
Takes the value out of the option, leaving a None
in its place.
Examples
let mut x = Some(2); let y = x.take(); assert_eq!(x, None); assert_eq!(y, Some(2)); let mut x: Option<u32> = None; let y = x.take(); assert_eq!(x, None); assert_eq!(y, None);
pub fn replace(&mut self, value: T) -> Option<T>
1.31.0[src]
Replaces the actual value in the option by the value given in parameter,
returning the old value if present,
leaving a Some
in its place without deinitializing either one.
Examples
let mut x = Some(2); let old = x.replace(5); assert_eq!(x, Some(5)); assert_eq!(old, Some(2)); let mut x = None; let old = x.replace(3); assert_eq!(x, Some(3)); assert_eq!(old, None);
pub fn deref(&self) -> Option<&<T as Deref>::Target>
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🔬 This is a nightly-only experimental API. (inner_deref
)
newly added
Converts from &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
.
Trait Implementations
impl<'_, T> Drop for OptionProxy<'_, T>
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impl<'_, T> DerefMut for OptionProxy<'_, T>
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impl<'_, T> Deref for OptionProxy<'_, T>
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Auto Trait Implementations
impl<'a, T> !Sync for OptionProxy<'a, T>
impl<'a, T> !Send for OptionProxy<'a, T>
impl<'a, T> Unpin for OptionProxy<'a, T> where
T: Unpin,
T: Unpin,
impl<'a, T> !RefUnwindSafe for OptionProxy<'a, T>
impl<'a, T> !UnwindSafe for OptionProxy<'a, T>
Blanket Implementations
impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,