Enum st8b7c:f320:99b9:690f:4595:cd17:293a:c069option8b7c:f320:99b9:690f:4595:cd17:293a:c069Option
pub enum Option<T> {
    None,
    Some(T),
}
The Option type. See the module level documentation for more. Variants
None
No value. Some(T)
Some value of type T. Implementations

sourceimpl<T> Option<T>
sourceconst: 1.48.0 · pub const 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); 
sourcepub fn is_some_and(&self, f: impl FnOnce(&T) -> bool) -> bool
🔬This is a nightly-only experimental API. (is_some_with #93050)

Returns true if the option is a Some and the value inside of it matches a predicate. Examples #![feature(is_some_with)]

let x: Option<u32> = Some(2);
assert_eq!(x.is_some_and(|&x| x > 1), true);

let x: Option<u32> = Some(0);
assert_eq!(x.is_some_and(|&x| x > 1), false);

let x: Option<u32> = None;
assert_eq!(x.is_some_and(|&x| x > 1), false); 
sourceconst: 1.48.0 · pub const 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); 
sourceconst: 1.48.0 · pub const 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:?}"); 
sourceconst: unstable · pub fn as_mut(&mut self) -> Option<&mut T>
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)); 
source1.33.0 (const: unstable) · pub fn as_pin_ref(self: Pin<&Option<T>>) -> Option<Pin<&T>>
Converts from Pin<&Option<T>> to Option<Pin<&T>>. 
source1.33.0 (const: unstable) · 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>>. 
sourceconst: unstable · pub fn expect(self, msg: &str) -> T
Returns the contained Some value, consuming the self value. Panics Panics if the value is a None with a custom panic message provided by msg. Examples let x = Some("value");
assert_eq!(x.expect("fruits are healthy"), "value"); ⓘlet x: Option<&str> = None;
x.expect("fruits are healthy"); // panics with `fruits are healthy`
 Recommended Message Style We recommend that expect messages are used to describe the reason you expect the Option should be Some. ⓘlet item = slice.get(0)
    .expect("slice should not be empty");
 Hint: If you’re having trouble remembering how to phrase expect error messages remember to focus on the word “should” as in “env variable should be set by blah” or “the given binary should be available and executable by the current user”. For more detail on expect message styles and the reasoning behind our recommendation please refer to the section on “Common Message Styles” in the st8b7c:f320:99b9:690f:4595:cd17:293a:c069error module docs. 
sourceconst: unstable · pub fn unwrap(self) -> T
Returns the contained Some value, consuming the self value. Because this function may panic, its use is generally discouraged. Instead, prefer to use pattern matching and handle the None case explicitly, or call unwrap_or, unwrap_or_else, or unwrap_or_default. Panics Panics if the self value equals None. Examples let x = Some("air");
assert_eq!(x.unwrap(), "air"); ⓘlet x: Option<&str> = None;
assert_eq!(x.unwrap(), "air"); // fails
 
sourceconst: unstable · pub fn unwrap_or(self, default: T) -> T
Returns the contained Some value or a provided default. Arguments passed to unwrap_or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use unwrap_or_else, which is lazily evaluated. Examples assert_eq!(Some("car").unwrap_or("bike"), "car");
assert_eq!(None.unwrap_or("bike"), "bike"); 
sourceconst: unstable · pub fn unwrap_or_else<F>(self, f: F) -> Twhere F: FnOnce() -> T,

Returns the contained Some value or computes it from a closure. Examples let k = 10;
assert_eq!(Some(4).unwrap_or_else(|| 2 * k), 4);
assert_eq!(None.unwrap_or_else(|| 2 * k), 20); 
sourceconst: unstable · pub fn unwrap_or_default(self) -> Twhere T: Default,

Returns the contained Some value or a default. Consumes the self argument then, if Some, returns the contained value, otherwise if None, returns the default value for that type. Examples Converts a string to an integer, turning poorly-formed strings into 0 (the default value for integers). parse converts a string to any other type that implements FromStr, returning None on error. let good_year_from_input = "1909";
let bad_year_from_input = "190blarg";
let good_year = good_year_from_input.parse().ok().unwrap_or_default();
let bad_year = bad_year_from_input.parse().ok().unwrap_or_default();

assert_eq!(1909, good_year);
assert_eq!(0, bad_year); 
source1.58.0 (const: unstable) · pub unsafe fn unwrap_unchecked(self) -> T
Returns the contained Some value, consuming the self value, without checking that the value is not None. Safety Calling this method on None is undefined behavior. Examples let x = Some("air");
assert_eq!(unsafe { x.unwrap_unchecked() }, "air"); let x: Option<&str> = None;
assert_eq!(unsafe { x.unwrap_unchecked() }, "air"); // Undefined behavior! 
sourceconst: unstable · pub fn map<U, F>(self, f: F) -> Option<U>where F: FnOnce(T) -> U,

Maps an Option<T> to Option<U> by applying a function to a contained value. Examples Converts an Option<String> into an Option<usize>, consuming the original: let maybe_some_string = Some(String8b7c:f320:99b9:690f:4595:cd17:293a:c069rom("Hello, World!"));
// `Option8b7c:f320:99b9:690f:4595:cd17:293a:c069map` takes self *by value*, consuming `maybe_some_string`
let maybe_some_len = maybe_some_string.map(|s| s.len());

assert_eq!(maybe_some_len, Some(13)); 
sourceconst: unstable · pub fn inspect<F>(self, f: F) -> Option<T>where F: FnOnce(&T),

🔬This is a nightly-only experimental API. (result_option_inspect #91345)

Calls the provided closure with a reference to the contained value (if Some). Examples #![feature(result_option_inspect)]

let v = vec![1, 2, 3, 4, 5];

// prints "got: 4"
let x: Option<&usize> = v.get(3).inspect(|x| println!("got: {x}"));

// prints nothing
let x: Option<&usize> = v.get(5).inspect(|x| println!("got: {x}")); 
sourceconst: unstable · pub fn map_or<U, F>(self, default: U, f: F) -> Uwhere F: FnOnce(T) -> U,

Returns the provided default result (if none), or applies a function to the contained value (if any). Arguments passed to map_or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use map_or_else, which is lazily evaluated. Examples let x = Some("foo");
assert_eq!(x.map_or(42, |v| v.len()), 3);

let x: Option<&str> = None;
assert_eq!(x.map_or(42, |v| v.len()), 42); 
sourceconst: unstable · pub fn map_or_else<U, D, F>(self, default: D, f: F) -> Uwhere D: FnOnce() -> U, F: FnOnce(T) -> U,

Computes a default function result (if none), or applies a different function to the contained value (if any). Examples let k = 21;

let x = Some("foo");
assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 3);

let x: Option<&str> = None;
assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 42); 
sourceconst: unstable · pub fn ok_or<E>(self, err: E) -> Result<T, E>
Transforms the Option<T> into a Result<T, E>, mapping Some(v) to Ok(v) and None to Err(err). Arguments passed to ok_or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use ok_or_else, which is lazily evaluated. Examples let x = Some("foo");
assert_eq!(x.ok_or(0), Ok("foo"));

let x: Option<&str> = None;
assert_eq!(x.ok_or(0), Err(0)); 
sourceconst: unstable · pub fn ok_or_else<E, F>(self, err: F) -> Result<T, E>where F: FnOnce() -> E,

Transforms the Option<T> into a Result<T, E>, mapping Some(v) to Ok(v) and None to Err(err()). Examples let x = Some("foo");
assert_eq!(x.ok_or_else(|| 0), Ok("foo"));

let x: Option<&str> = None;
assert_eq!(x.ok_or_else(|| 0), Err(0)); 
source1.40.0 (const: unstable) · pub fn as_deref(&self) -> Option<&<T as Deref>8b7c:f320:99b9:690f:4595:cd17:293a:c069Target>where T: Deref,

Converts from Option<T> (or &Option<T>) to Option<&T8b7c:f320:99b9:690f:4595:cd17:293a:c069Target>. 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); 
source1.40.0 (const: unstable) · pub fn as_deref_mut(&mut self) -> Option<&mut <T as Deref>8b7c:f320:99b9:690f:4595:cd17:293a:c069Target>where T: DerefMut,

Converts from Option<T> (or &mut Option<T>) to Option<&mut T8b7c:f320:99b9:690f:4595:cd17:293a:c069Target>. Leaves the original Option in-place, creating a new one containing a mutable reference to the inner type’s Der8b7c:f320:99b9:690f:4595:cd17:293a:c069Target type. Examples let mut x: Option<String> = Some("hey".to_owned());
assert_eq!(x.as_deref_mut().map(|x| {
    x.make_ascii_uppercase();
    x
}), Some("HEY".to_owned().as_mut_str())); 
sourceconst: unstable · pub fn iter(&self) -> Iter<'_, T>Notable traits for Iter<'a, A>impl<'a, A> Iterator for Iter<'a, A>
    type Item = &'a A;

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); 
sourcepub fn iter_mut(&mut self) -> IterMut<'_, T>Notable traits for IterMut<'a, A>impl<'a, A> Iterator for IterMut<'a, A>
    type Item = &'a mut A;

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); 
sourceconst: unstable · pub fn and<U>(self, optb: Option<U>) -> Option<U>
Returns None if the option is None, otherwise returns optb. Arguments passed to and are eagerly evaluated; if you are passing the result of a function call, it is recommended to use and_then, which is lazily evaluated. Examples let x = Some(2);
let y: Option<&str> = None;
assert_eq!(x.and(y), None);

let x: Option<u32> = None;
let y = Some("foo");
assert_eq!(x.and(y), None);

let x = Some(2);
let y = Some("foo");
assert_eq!(x.and(y), Some("foo"));

let x: Option<u32> = None;
let y: Option<&str> = None;
assert_eq!(x.and(y), None); 
sourceconst: unstable · pub fn and_then<U, F>(self, f: F) -> Option<U>where F: FnOnce(T) -> Option<U>,

Returns None if the option is None, otherwise calls f with the wrapped value and returns the result. Some languages call this operation flatmap. Examples fn sq_then_to_string(x: u32) -> Option<String> {
    x.checked_mul(x).map(|sq| sq.to_string())
}

assert_eq!(Some(2).and_then(sq_then_to_string), Some(4.to_string()));
assert_eq!(Some(1_000_000).and_then(sq_then_to_string), None); // overflowed!
assert_eq!(None.and_then(sq_then_to_string), None); Often used to chain fallible operations that may return None. let arr_2d = [["A0", "A1"], ["B0", "B1"]];

let item_0_1 = arr_2d.get(0).and_then(|row| row.get(1));
assert_eq!(item_0_1, Some(&"A1"));

let item_2_0 = arr_2d.get(2).and_then(|row| row.get(0));
assert_eq!(item_2_0, None); 
source1.27.0 (const: unstable) · pub fn filter<P>(self, predicate: P) -> Option<T>where P: FnOnce(&T) -> bool,

Returns None if the option is None, otherwise calls predicate with the wrapped value and returns:  
Some(t) if predicate returns true (where t is the wrapped value), and 
None if predicate returns false.  This function works similar to Iterator8b7c:f320:99b9:690f:4595:cd17:293a:c069ilter(). You can imagine the Option<T> being an iterator over one or zero elements. filter() lets you decide which elements to keep. Examples fn is_even(n: &i32) -> bool {
    n % 2 == 0
}

assert_eq!(None.filter(is_even), None);
assert_eq!(Some(3).filter(is_even), None);
assert_eq!(Some(4).filter(is_even), Some(4)); 
sourceconst: unstable · pub fn or(self, optb: Option<T>) -> Option<T>
Returns the option if it contains a value, otherwise returns optb. Arguments passed to or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use or_else, which is lazily evaluated. Examples let x = Some(2);
let y = None;
assert_eq!(x.or(y), Some(2));

let x = None;
let y = Some(100);
assert_eq!(x.or(y), Some(100));

let x = Some(2);
let y = Some(100);
assert_eq!(x.or(y), Some(2));

let x: Option<u32> = None;
let y = None;
assert_eq!(x.or(y), None); 
sourceconst: unstable · pub fn or_else<F>(self, f: F) -> Option<T>where F: FnOnce() -> Option<T>,

Returns the option if it contains a value, otherwise calls f and returns the result. Examples fn nobody() -> Option<&'static str> { None }
fn vikings() -> Option<&'static str> { Some("vikings") }

assert_eq!(Some("barbarians").or_else(vikings), Some("barbarians"));
assert_eq!(None.or_else(vikings), Some("vikings"));
assert_eq!(None.or_else(nobody), None); 
source1.37.0 (const: unstable) · pub fn xor(self, optb: Option<T>) -> Option<T>
Returns Some if exactly one of self, optb is Some, otherwise returns None. Examples let x = Some(2);
let y: Option<u32> = None;
assert_eq!(x.xor(y), Some(2));

let x: Option<u32> = None;
let y = Some(2);
assert_eq!(x.xor(y), Some(2));

let x = Some(2);
let y = Some(2);
assert_eq!(x.xor(y), None);

let x: Option<u32> = None;
let y: Option<u32> = None;
assert_eq!(x.xor(y), None); 
source1.53.0 (const: unstable) · pub fn insert(&mut self, value: T) -> &mut T
Inserts value into the option, then returns a mutable reference to it. If the option already contains a value, the old value is dropped. See also Option8b7c:f320:99b9:690f:4595:cd17:293a:c069get_or_insert, which doesn’t update the value if the option already contains Some. Example let mut opt = None;
let val = opt.insert(1);
assert_eq!(*val, 1);
assert_eq!(opt.unwrap(), 1);
let val = opt.insert(2);
assert_eq!(*val, 2);
*val = 3;
assert_eq!(opt.unwrap(), 3); 
source1.20.0 (const: unstable) · pub fn get_or_insert(&mut self, value: T) -> &mut T
Inserts value into the option if it is None, then returns a mutable reference to the contained value. See also Option8b7c:f320:99b9:690f:4595:cd17:293a:c069insert, which updates the value even if the option already contains Some. 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)); 
sourceconst: unstable · pub fn get_or_insert_default(&mut self) -> &mut Twhere T: Default,

🔬This is a nightly-only experimental API. (option_get_or_insert_default #82901)

Inserts the default value into the option if it is None, then returns a mutable reference to the contained value. Examples #![feature(option_get_or_insert_default)]

let mut x = None;

{
    let y: &mut u32 = x.get_or_insert_default();
    assert_eq!(y, &0);

    *y = 7;
}

assert_eq!(x, Some(7)); 
source1.20.0 (const: unstable) · pub fn get_or_insert_with<F>(&mut self, f: F) -> &mut Twhere 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)); 
sourceconst: unstable · pub fn take(&mut self) -> Option<T>
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); 
source1.31.0 (const: unstable) · pub fn replace(&mut self, value: T) -> Option<T>
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); 
sourceconst: unstable · pub fn contains<U>(&self, x: &U) -> boolwhere U: PartialEq<T>,

🔬This is a nightly-only experimental API. (option_result_contains #62358)

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); 
source1.46.0 (const: unstable) · pub fn zip<U>(self, other: Option<U>) -> Option<(T, U)>
Zips self with another Option. If self is Some(s) and other is Some(o), this method returns Some((s, o)). Otherwise, None is returned. Examples let x = Some(1);
let y = Some("hi");
let z = Non8b7c:f320:99b9:690f:4595:cd17:293a:c069<u8>;

assert_eq!(x.zip(y), Some((1, "hi")));
assert_eq!(x.zip(z), None); 
sourceconst: unstable · pub fn zip_with<U, F, R>(self, other: Option<U>, f: F) -> Option<R>where F: FnOnce(T, U) -> R,

🔬This is a nightly-only experimental API. (option_zip #70086)

Zips self and another Option with function f. If self is Some(s) and other is Some(o), this method returns Some(f(s, o)). Otherwise, None is returned. Examples #![feature(option_zip)]

#[derive(Debug, PartialEq)]
struct Point {
    x: f64,
    y: f64,
}

impl Point {
    fn new(x: f64, y: f64) -> Self {
        Self { x, y }
    }
}

let x = Some(17.5);
let y = Some(42.7);

assert_eq!(x.zip_with(y, Point8b7c:f320:99b9:690f:4595:cd17:293a:c069new), Some(Point { x: 17.5, y: 42.7 }));
assert_eq!(x.zip_with(None, Point8b7c:f320:99b9:690f:4595:cd17:293a:c069new), None); 

sourceimpl<T, U> Option<(T, U)>
sourcepub const fn unzip(self) -> (Option<T>, Option<U>)
🔬This is a nightly-only experimental API. (unzip_option #87800)

Unzips an option containing a tuple of two options. If self is Some((a, b)) this method returns (Some(a), Some(b)). Otherwise, (None, None) is returned. Examples #![feature(unzip_option)]

let x = Some((1, "hi"));
let y = Non8b7c:f320:99b9:690f:4595:cd17:293a:c069<(u8, u32)>;

assert_eq!(x.unzip(), (Some(1), Some("hi")));
assert_eq!(y.unzip(), (None, None)); 

sourceimpl<T> Option<&T>
source1.35.0 (const: unstable) · pub fn copied(self) -> Option<T>where T: Copy,

Maps an Option<&T> to an Option<T> by copying the contents of the option. Examples let x = 12;
let opt_x = Some(&x);
assert_eq!(opt_x, Some(&12));
let copied = opt_x.copied();
assert_eq!(copied, Some(12)); 
sourceconst: unstable · pub fn cloned(self) -> Option<T>where T: Clone,

Maps an Option<&T> to an Option<T> by cloning the contents of the option. Examples let x = 12;
let opt_x = Some(&x);
assert_eq!(opt_x, Some(&12));
let cloned = opt_x.cloned();
assert_eq!(cloned, Some(12)); 

sourceimpl<T> Option<&mut T>
source1.35.0 (const: unstable) · pub fn copied(self) -> Option<T>where T: Copy,

Maps an Option<&mut T> to an Option<T> by copying the contents of the option. Examples let mut x = 12;
let opt_x = Some(&mut x);
assert_eq!(opt_x, Some(&mut 12));
let copied = opt_x.copied();
assert_eq!(copied, Some(12)); 
source1.26.0 (const: unstable) · pub fn cloned(self) -> Option<T>where T: Clone,

Maps an Option<&mut T> to an Option<T> by cloning the contents of the option. Examples let mut x = 12;
let opt_x = Some(&mut x);
assert_eq!(opt_x, Some(&mut 12));
let cloned = opt_x.cloned();
assert_eq!(cloned, Some(12)); 

sourceimpl<T, E> Option<Result<T, E>>
source1.33.0 (const: unstable) · pub fn transpose(self) -> Result<Option<T>, E>
Transposes an Option of a Result into a Result of an Option. None will be mapped to Ok(None). Some(Ok(_)) and Some(Err(_)) will be mapped to Ok(Some(_)) and Err(_). Examples #[derive(Debug, Eq, PartialEq)]
struct SomeErr;

let x: Result<Option<i32>, SomeErr> = Ok(Some(5));
let y: Option<Result<i32, SomeErr>> = Some(Ok(5));
assert_eq!(x, y.transpose()); 

sourceimpl<T> Option<Option<T>>
source1.40.0 (const: unstable) · pub fn flatten(self) -> Option<T>
Converts from Option<Option<T>> to Option<T>. Examples Basic usage: let x: Option<Option<u32>> = Some(Some(6));
assert_eq!(Some(6), x.flatten());

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

let x: Option<Option<u32>> = None;
assert_eq!(None, x.flatten()); Flattening only removes one level of nesting at a time: let x: Option<Option<Option<u32>>> = Some(Some(Some(6)));
assert_eq!(Some(Some(6)), x.flatten());
assert_eq!(Some(6), x.flatten().flatten()); 


Trait Implementations

sourceconst: unstable · impl<T> Clone for Option<T>where T: Clone,

sourceconst: unstable · fn clone(&self) -> Option<T>Returns a copy of the value. Read more

sourceconst: unstable · fn clone_from(&mut self, source: &Option<T>)Performs copy-assignment from source. Read more


sourceimpl<T> Debug for Option<T>where T: Debug,

sourcefn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>Formats the value using the given formatter. Read more


sourceconst: unstable · impl<T> Default for Option<T>
sourceconst: unstable · fn default() -> Option<T>
Returns None. Examples let opt: Option<u32> = Option8b7c:f320:99b9:690f:4595:cd17:293a:c069ult();
assert!(opt.is_none()); 

source1.30.0 (const: unstable) · impl<'a, T> From<&'a Option<T>> for Option<&'a T>
sourceconst: unstable · fn from(o: &'a Option<T>) -> Option<&'a 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 from to first take an Option to a reference to the value inside the original. let s: Option<String> = Some(String8b7c:f320:99b9:690f:4595:cd17:293a:c069rom("Hello, Rustaceans!"));
let o: Option<usize> = Option8b7c:f320:99b9:690f:4595:cd17:293a:c069rom(&s).map(|ss: &String| ss.len());

println!("Can still print s: {s:?}");

assert_eq!(o, Some(18)); 

source1.30.0 (const: unstable) · impl<'a, T> From<&'a mut Option<T>> for Option<&'a mut T>
sourceconst: unstable · fn from(o: &'a mut Option<T>) -> Option<&'a mut T>
Converts from &mut Option<T> to Option<&mut T> Examples let mut s = Some(String8b7c:f320:99b9:690f:4595:cd17:293a:c069rom("Hello"));
let o: Option<&mut String> = Option8b7c:f320:99b9:690f:4595:cd17:293a:c069rom(&mut s);

match o {
    Some(t) => *t = String8b7c:f320:99b9:690f:4595:cd17:293a:c069rom("Hello, Rustaceans!"),
    None => (),
}

assert_eq!(s, Some(String8b7c:f320:99b9:690f:4595:cd17:293a:c069rom("Hello, Rustaceans!"))); 

source1.12.0 (const: unstable) · impl<T> From<T> for Option<T>
sourceconst: unstable · fn from(val: T) -> Option<T>
Moves val into a new Some. Examples let o: Option<u8> = Option8b7c:f320:99b9:690f:4595:cd17:293a:c069rom(67);

assert_eq!(Some(67), o); 

sourceimpl<A, V> FromIterator<Option<A>> for Option<V>where V: FromIterator<A>,

sourcefn from_iter<I>(iter: I) -> Option<V>where I: IntoIterator<Item = Option<A>>,

Takes each element in the Iterator: if it is None, no further elements are taken, and the None is returned. Should no None occur, a container of type V containing the values of each Option is returned. Examples Here is an example which increments every integer in a vector. We use the checked variant of add that returns None when the calculation would result in an overflow. let items = vec![0_u16, 1, 2];

let res: Option<Vec<u16>> = items
    .iter()
    .map(|x| x.checked_add(1))
    .collect();

assert_eq!(res, Some(vec![1, 2, 3])); As you can see, this will return the expected, valid items. Here is another example that tries to subtract one from another list of integers, this time checking for underflow: let items = vec![2_u16, 1, 0];

let res: Option<Vec<u16>> = items
    .iter()
    .map(|x| x.checked_sub(1))
    .collect();

assert_eq!(res, None); Since the last element is zero, it would underflow. Thus, the resulting value is None. Here is a variation on the previous example, showing that no further elements are taken from iter after the first None. let items = vec![3_u16, 2, 1, 10];

let mut shared = 0;

let res: Option<Vec<u16>> = items
    .iter()
    .map(|x| { shared += x; x.checked_sub(2) })
    .collect();

assert_eq!(res, None);
assert_eq!(shared, 6); Since the third element caused an underflow, no further elements were taken, so the final value of shared is 6 (= 3 + 2 + 1), not 16. 

sourceconst: unstable · impl<T> FromResidual<<Option<T> as Try>8b7c:f320:99b9:690f:4595:cd17:293a:c069Residual> for Option<T>
sourceconst: unstable · fn from_residual(residual: Option<Infallible>) -> Option<T>
🔬This is a nightly-only experimental API. (try_trait_v2 #84277)
Constructs the type from a compatible Residual type. Read more


sourceimpl<T> FromResidual<Yeet<()>> for Option<T>
sourcefn from_residual(Yeet<()>) -> Option<T>
🔬This is a nightly-only experimental API. (try_trait_v2 #84277)
Constructs the type from a compatible Residual type. Read more


sourceimpl<T> Hash for Option<T>where T: Hash,

sourcefn hash<__H>(&self, state: &mut __H)where __H: Hasher,
Feeds this value into the given Hasher. Read more

source1.3.0 · fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher,
Feeds a slice of this type into the given Hasher. Read more


source1.4.0 · impl<'a, T> IntoIterator for &'a Option<T>
type Item = &'a TThe type of the elements being iterated over.
type IntoIter = Iter<'a, T>Which kind of iterator are we turning this into?
sourcefn into_iter(self) -> Iter<'a, T>Notable traits for Iter<'a, A>impl<'a, A> Iterator for Iter<'a, A>
    type Item = &'a A;
Creates an iterator from a value. Read more


source1.4.0 · impl<'a, T> IntoIterator for &'a mut Option<T>
type Item = &'a mut TThe type of the elements being iterated over.
type IntoIter = IterMut<'a, T>Which kind of iterator are we turning this into?
sourcefn into_iter(self) -> IterMut<'a, T>Notable traits for IterMut<'a, A>impl<'a, A> Iterator for IterMut<'a, A>
    type Item = &'a mut A;
Creates an iterator from a value. Read more


sourceimpl<T> IntoIterator for Option<T>
sourcefn into_iter(self) -> IntoIter<T>Notable traits for IntoIter<A>impl<A> Iterator for IntoIter<A>
    type Item = A;

Returns a consuming iterator over the possibly contained value. Examples let x = Some("string");
let v: Vec<&str> = x.into_iter().collect();
assert_eq!(v, ["string"]);

let x = None;
let v: Vec<&str> = x.into_iter().collect();
assert!(v.is_empty()); 
type Item = TThe type of the elements being iterated over.
type IntoIter = IntoIter<T>Which kind of iterator are we turning this into?

sourceimpl<T> Ord for Option<T>where T: Ord,

sourcefn cmp(&self, other: &Option<T>) -> OrderingThis method returns an Ordering between self and other. Read more

source1.21.0 · fn max(self, other: Self) -> SelfCompares and returns the maximum of two values. Read more

source1.21.0 · fn min(self, other: Self) -> SelfCompares and returns the minimum of two values. Read more

source1.50.0 · fn clamp(self, min: Self, max: Self) -> Selfwhere Self: PartialOrd<Self>,
Restrict a value to a certain interval. Read more


sourceimpl<T> PartialEq<Option<T>> for Option<T>where T: PartialEq<T>,

sourcefn eq(&self, other: &Option<T>) -> boolThis method tests for self and other values to be equal, and is used by ==. Read more

sourcefn ne(&self, other: &Rhs) -> boolThis method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more


sourceimpl<T> PartialOrd<Option<T>> for Option<T>where T: PartialOrd<T>,

sourcefn partial_cmp(&self, other: &Option<T>) -> Option<Ordering>This method returns an ordering between self and other values if one exists. Read more

sourcefn lt(&self, other: &Rhs) -> boolThis method tests less than (for self and other) and is used by the < operator. Read more

sourcefn le(&self, other: &Rhs) -> boolThis method tests less than or equal to (for self and other) and is used by the <= operator. Read more

sourcefn gt(&self, other: &Rhs) -> boolThis method tests greater than (for self and other) and is used by the > operator. Read more

sourcefn ge(&self, other: &Rhs) -> boolThis method tests greater than or equal to (for self and other) and is used by the >= operator. Read more


source1.37.0 · impl<T, U> Product<Option<U>> for Option<T>where T: Product<U>,

sourcefn product<I>(iter: I) -> Option<T>where I: Iterator<Item = Option<U>>,

Takes each element in the Iterator: if it is a None, no further elements are taken, and the None is returned. Should no None occur, the product of all elements is returned. 

sourceimpl<T> Residual<T> for Option<Infallible>
type TryType = Option<T>
🔬This is a nightly-only experimental API. (try_trait_v2_residual #91285)
The “return” type of this meta-function.

source1.37.0 · impl<T, U> Sum<Option<U>> for Option<T>where T: Sum<U>,

sourcefn sum<I>(iter: I) -> Option<T>where I: Iterator<Item = Option<U>>,

Takes each element in the Iterator: if it is a None, no further elements are taken, and the None is returned. Should no None occur, the sum of all elements is returned. Examples This sums up the position of the character ‘a’ in a vector of strings, if a word did not have the character ‘a’ the operation returns None: let words = vec!["have", "a", "great", "day"];
let total: Option<usize> = words.iter().map(|w| w.find('a')).sum();
assert_eq!(total, Some(5)); 

sourceconst: unstable · impl<T> Try for Option<T>
type Output = T
🔬This is a nightly-only experimental API. (try_trait_v2 #84277)
The type of the value produced by ? when not short-circuiting.
type Residual = Option<Infallible>
🔬This is a nightly-only experimental API. (try_trait_v2 #84277)
The type of the value passed to FromResidual8b7c:f320:99b9:690f:4595:cd17:293a:c069rom_residual as part of ? when short-circuiting. Read more

sourceconst: unstable · fn from_output(output: <Option<T> as Try>8b7c:f320:99b9:690f:4595:cd17:293a:c069Output) -> Option<T>
🔬This is a nightly-only experimental API. (try_trait_v2 #84277)
Constructs the type from its Output type. Read more

sourceconst: unstable · fn branch( self) -> ControlFlow<<Option<T> as Try>8b7c:f320:99b9:690f:4595:cd17:293a:c069Residual, <Option<T> as Try>8b7c:f320:99b9:690f:4595:cd17:293a:c069Output>
🔬This is a nightly-only experimental API. (try_trait_v2 #84277)
Used in ? to decide whether the operator should produce a value (because this returned ControlFlow8b7c:f320:99b9:690f:4595:cd17:293a:c069ontinue) or propagate a value back to the caller (because this returned ControlFlow8b7c:f320:99b9:690f:4595:cd17:293a:c069reak). Read more


sourceimpl<T> Copy for Option<T>where T: Copy,
sourceimpl<T> Eq for Option<T>where T: Eq,
sourceimpl<T> StructuralEq for Option<T>sourceimpl<T> StructuralPartialEq for Option<T>

Auto Trait Implementations

impl<T> RefUnwindSafe for Option<T>where T: RefUnwindSafe,
impl<T> Send for Option<T>where T: Send,
impl<T> Sync for Option<T>where T: Sync,
impl<T> Unpin for Option<T>where T: Unpin,
impl<T> UnwindSafe for Option<T>where T: UnwindSafe,


Blanket Implementations

sourceimpl<T> Any for Twhere T: 'static + ?Sized,

sourcefn type_id(&self) -> TypeIdGets the TypeId of self. Read more


sourceimpl<T> Borrow<T> for Twhere T: ?Sized,

sourceconst: unstable · fn borrow(&self) -> &TImmutably borrows from an owned value. Read more


sourceimpl<T> BorrowMut<T> for Twhere T: ?Sized,

sourceconst: unstable · fn borrow_mut(&mut self) -> &mut TMutably borrows from an owned value. Read more


sourceimpl<T> From<!> for T
sourceconst: unstable · fn from(t: !) -> TConverts to this type from the input type.

sourceimpl<T> From<T> for T
sourceconst: unstable · fn from(t: T) -> T
Returns the argument unchanged. 

sourceimpl<T, U> Into<U> for Twhere U: From<T>,

sourceconst: unstable · fn into(self) -> U
Calls U8b7c:f320:99b9:690f:4595:cd17:293a:c069rom(self). That is, this conversion is whatever the implementation of From<T> for U chooses to do. 

sourceimpl<T> ToOwned for Twhere T: Clone,

type Owned = TThe resulting type after obtaining ownership.
sourcefn to_owned(&self) -> TCreates owned data from borrowed data, usually by cloning. Read more

sourcefn clone_into(&self, target: &mut T)Uses borrowed data to replace owned data, usually by cloning. Read more


sourceimpl<T, U> TryFrom<U> for Twhere U: Into<T>,

type Error = InfallibleThe type returned in the event of a conversion error.
sourceconst: unstable · fn try_from(value: U) -> Result<T, <T as TryFrom<U>>8b7c:f320:99b9:690f:4595:cd17:293a:c069rror>Performs the conversion.

sourceimpl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

type Error = <U as TryFrom<T>>8b7c:f320:99b9:690f:4595:cd17:293a:c069rrorThe type returned in the event of a conversion error.
sourceconst: unstable · fn try_into(self) -> Result<U, <U as TryFrom<T>>8b7c:f320:99b9:690f:4595:cd17:293a:c069rror>Performs the conversion.



    
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