Type Alias Datum

pub type Datum = Option<ScalarImpl>;

Aliased Type

enum Datum {
    None,
    Some(ScalarImpl),
}

Variants

None

No value.

Some(ScalarImpl)

Some value of type T.

Implementations

impl<T> Option<T>

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);

pub fn is_some_and(self, f: impl FnOnce(T) -> bool) -> bool

Returns true if the option is a Some and the value inside of it matches a predicate.

Examples

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);

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);

pub fn is_none_or(self, f: impl FnOnce(T) -> bool) -> bool

Returns true if the option is a None or the value inside of it matches a predicate.

Examples

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

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

let x: Option<u32> = None;
assert_eq!(x.is_none_or(|x| x > 1), true);

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

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

Examples

Calculates the length of an Option<String> as an Option<usize> without moving the String. 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 const 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));

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

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

pub const 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 const fn as_slice(&self) -> &[T]

Returns a slice of the contained value, if any. If this is None, an empty slice is returned. This can be useful to have a single type of iterator over an Option or slice.

Note: Should you have an Option<&T> and wish to get a slice of T, you can unpack it via opt.map_or(&[], std::slice::from_ref).

Examples

assert_eq!(
    [Some(1234).as_slice(), None.as_slice()],
    [&[1234][..], &[][..]],
);

The inverse of this function is (discounting borrowing) [_]::first:

for i in [Some(1234_u16), None] {
    assert_eq!(i.as_ref(), i.as_slice().first());
}

pub const fn as_mut_slice(&mut self) -> &mut [T]

Returns a mutable slice of the contained value, if any. If this is None, an empty slice is returned. This can be useful to have a single type of iterator over an Option or slice.

Note: Should you have an Option<&mut T> instead of a &mut Option<T>, which this method takes, you can obtain a mutable slice via opt.map_or(&mut [], std::slice::from_mut).

Examples

assert_eq!(
    [Some(1234).as_mut_slice(), None.as_mut_slice()],
    [&mut [1234][..], &mut [][..]],
);

The result is a mutable slice of zero or one items that points into our original Option:

let mut x = Some(1234);
x.as_mut_slice()[0] += 1;
assert_eq!(x, Some(1235));

The inverse of this method (discounting borrowing) is [_]::first_mut:

assert_eq!(Some(123).as_mut_slice().first_mut(), Some(&mut 123))

pub const 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 std::error module docs.

pub const fn unwrap(self) -> T

Returns the contained Some value, consuming the self value.

Because this function may panic, its use is generally discouraged. Panics are meant for unrecoverable errors, and may abort the entire program.

Instead, prefer to use pattern matching and handle the None case explicitly, or call unwrap_or, unwrap_or_else, or unwrap_or_default. In functions returning Option, you can use the ? (try) operator.

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

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");

pub fn unwrap_or_else<F>(self, f: F) -> T

where 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);

pub fn unwrap_or_default(self) -> T

where 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

let x: Option<u32> = None;
let y: Option<u32> = Some(12);

assert_eq!(x.unwrap_or_default(), 0);
assert_eq!(y.unwrap_or_default(), 12);

pub const 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!

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 (if Some) or returns None (if None).

Examples

Calculates the length of an Option<String> as an Option<usize>, consuming the original:

let maybe_some_string = Some(String::from("Hello, World!"));
// `Option::map` 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));

let x: Option<&str> = None;
assert_eq!(x.map(|s| s.len()), None);

pub fn inspect<F>(self, f: F) -> Option<T>

where F: FnOnce(&T),

Calls a function with a reference to the contained value if Some.

Returns the original option.

Examples

let list = vec![1, 2, 3];

// prints "got: 2"
let x = list
    .get(1)
    .inspect(|x| println!("got: {x}"))
    .expect("list should be long enough");

// prints nothing
list.get(5).inspect(|x| println!("got: {x}"));

pub fn map_or<U, F>(self, default: U, f: F) -> U

where 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);

pub fn map_or_else<U, D, F>(self, default: D, f: F) -> U

where 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).

Basic 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);

Handling a Result-based fallback

A somewhat common occurrence when dealing with optional values in combination with Result<T, E> is the case where one wants to invoke a fallible fallback if the option is not present. This example parses a command line argument (if present), or the contents of a file to an integer. However, unlike accessing the command line argument, reading the file is fallible, so it must be wrapped with Ok.

let v: u64 = std::env::args()
   .nth(1)
   .map_or_else(|| std::fs::read_to_string("/etc/someconfig.conf"), Ok)?
   .parse()?;

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));

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));

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);

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

where T: DerefMut,

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

Leaves the original Option in-place, creating a new one containing a mutable reference to the inner type’s Deref::Target 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()));

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

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 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);

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);

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 Iterator::filter(). 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));

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);

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);

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);

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 Option::get_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);

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 Option::insert, 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));

pub fn get_or_insert_default(&mut self) -> &mut T

where T: Default,

Inserts the default value 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_default();
    assert_eq!(y, &0);

    *y = 7;
}

assert_eq!(x, Some(7));

pub fn get_or_insert_with<F>(&mut self, f: F) -> &mut T

where 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 const 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);

pub fn take_if<P>(&mut self, predicate: P) -> Option<T>

where P: FnOnce(&mut T) -> bool,

Takes the value out of the option, but only if the predicate evaluates to true on a mutable reference to the value.

In other words, replaces self with None if the predicate returns true. This method operates similar to Option::take but conditional.

Examples

let mut x = Some(42);

let prev = x.take_if(|v| if *v == 42 {
    *v += 1;
    false
} else {
    false
});
assert_eq!(x, Some(43));
assert_eq!(prev, None);

let prev = x.take_if(|v| *v == 43);
assert_eq!(x, None);
assert_eq!(prev, Some(43));

pub const 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);

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 = None::<u8>;

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

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)

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, Point::new), Some(Point { x: 17.5, y: 42.7 }));
assert_eq!(x.zip_with(None, Point::new), None);

Trait Implementations

impl<T> ApproxEq for Option<T>

where T: Copy + ApproxEq,

type Margin = <T as ApproxEq>::Margin

This type type defines a margin within which two values are to be considered approximately equal. It must implement Default so that approx_eq() can be called on unknown types.

fn approx_eq<M>(self, other: Option<T>, margin: M) -> bool

where M: Into<<Option<T> as ApproxEq>::Margin>,

This method tests that the self and other values are equal within margin of each other.

fn approx_ne<M>(self, other: Self, margin: M) -> bool

where M: Into<Self::Margin>,

This method tests that the self and other values are not within margin of each other.

impl<P> BlockingList for Option<P>

where P: BlockingList,

fn next(&mut self) -> Result<Option<Entry>, Error>

Fetch a new page of [Entry]

impl<P> BlockingList for Option<P>

where P: BlockingList,

fn next(&mut self) -> Result<Option<Entry>, Error>

Fetch a new page of [Entry]

impl<'de, T> BorrowDecode<'de> for Option<T>

where T: BorrowDecode<'de>,

fn borrow_decode<D>(decoder: &mut D) -> Result<Option<T>, DecodeError>

where D: BorrowDecoder<'de>,

Attempt to decode this type with the given BorrowDecode.

impl<T> Clear for Option<T>

fn clear(&mut self)

Clear all data in self, retaining the allocated capacithy.

impl<T> Clear for Option<T>

fn clear(&mut self)

Clear this make, make it equivalent to newly created object.

impl<T> Clone for Option<T>

where T: Clone,

fn clone(&self) -> Option<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Option<T>)

Performs copy-assignment from source.

impl<F> ConfigField for Option<F>

where F: ConfigField + Default,

fn visit<V>(&self, v: &mut V, key: &str, description: &'static str)

where V: Visit,

fn set(&mut self, key: &str, value: &str) -> Result<(), DataFusionError>

impl<T> Context<T, Infallible> for Option<T>

use anyhow::{Context, Result};

fn maybe_get() -> Option<T> {
    ...
}

fn demo() -> Result<()> {
    let t = maybe_get().context("there is no T")?;
    ...
}

fn context<C>(self, context: C) -> Result<T, Error>

where C: Display + Send + Sync + 'static,

Wrap the error value with additional context.

fn with_context<C, F>(self, context: F) -> Result<T, Error>

where C: Display + Send + Sync + 'static, F: FnOnce() -> C,

Wrap the error value with additional context that is evaluated lazily only once an error does occur.

impl DatumFromProtoExt for Option<ScalarImpl>

fn from_protobuf( proto: &Datum, data_type: &DataType, ) -> Result<Option<ScalarImpl>, ValueEncodingError>

Create a datum from the protobuf representation with the given data type.

impl<T> Debug for Option<T>

where T: Debug,

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

Formats the value using the given formatter.

impl<T> Decodable for Option<T>

where T: Decodable,

fn decode(value: &Value) -> Result<Option<T>, Error>

impl<T> Decodable for Option<T>

where T: Decodable,

fn decode_arrow(col: &dyn Array, row_no: usize) -> Result<Option<T>, Error>

impl<'a, T> Decode<'a> for Option<T>

where T: Choice<'a>,

fn decode<R>(reader: &mut R) -> Result<Option<T>, Error>

where R: Reader<'a>,

Attempt to decode this message using the provided decoder.

fn from_der(bytes: &'a [u8]) -> Result<Self, Error>

Parse Self from the provided DER-encoded byte slice.

impl<'a, T> Decode<'a> for Option<T>

where T: Choice<'a>,

fn decode<R>(reader: &mut R) -> Result<Option<T>, Error>

where R: Reader<'a>,

Attempt to decode this message using the provided decoder.

fn from_der(bytes: &'a [u8]) -> Result<Self, Error>

Parse Self from the provided DER-encoded byte slice.

impl<'r, DB, T> Decode<'r, DB> for Option<T>

where DB: Database, T: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<Option<T>, Box<dyn Error + Send + Sync>>

Decode a new value of this type using a raw value from the database.

impl<T> Decode for Option<T>

where T: Decode,

fn decode<D>(decoder: &mut D) -> Result<Option<T>, DecodeError>

where D: Decoder,

Attempt to decode this type with the given Decode.

impl<T> Default for Option<T>

fn default() -> Option<T>

Returns None.

Examples

let opt: Option<u32> = Option::default();
assert!(opt.is_none());

impl DefaultOrd for Option<ScalarImpl>

fn default_cmp(&self, other: &Option<ScalarImpl>) -> Ordering

impl DefaultPartialOrd for Option<ScalarImpl>

fn default_partial_cmp(&self, other: &Option<ScalarImpl>) -> Option<Ordering>

impl<T> DerOrd for Option<T>

where T: DerOrd,

fn der_cmp(&self, other: &Option<T>) -> Result<Ordering, Error>

Return an Ordering between self and other when serialized as ASN.1 DER.

impl<T> DerOrd for Option<T>

where T: DerOrd,

fn der_cmp(&self, other: &Option<T>) -> Result<Ordering, Error>

Return an Ordering between self and other when serialized as ASN.1 DER.

impl<'de, T> Deserialize<'de> for Option<T>

where T: Deserialize<'de>,

fn deserialize<D>( deserializer: D, ) -> Result<Option<T>, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<'de, T> Deserialize<'de> for Option<T>

where T: Deserialize<'de>,

fn deserialize<D>( deserializer: D, ) -> Result<Option<T>, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

impl<'de, T, U> DeserializeAs<'de, Option<T>> for Option<U>

where U: DeserializeAs<'de, T>,

fn deserialize_as<D>( deserializer: D, ) -> Result<Option<T>, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<'q, T> Encode<'q, Any> for Option<T>

where T: Encode<'q, Any> + 'q + Type<Any>,

fn encode_by_ref( &self, buf: &mut AnyArgumentBuffer<'q>, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

Writes the value of self into buf without moving self.

fn encode( self, buf: &mut <DB as Database>::ArgumentBuffer<'q>, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

where Self: Sized,

Writes the value of self into buf in the expected format for the database.

fn produces(&self) -> Option<<DB as Database>::TypeInfo>

fn size_hint(&self) -> usize

impl<'q, T> Encode<'q, MySql> for Option<T>

where T: Encode<'q, MySql> + Type<MySql> + 'q,

fn produces(&self) -> Option<<MySql as Database>::TypeInfo>

fn encode( self, buf: &mut <MySql as Database>::ArgumentBuffer<'q>, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

Writes the value of self into buf in the expected format for the database.

fn encode_by_ref( &self, buf: &mut <MySql as Database>::ArgumentBuffer<'q>, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

Writes the value of self into buf without moving self.

fn size_hint(&self) -> usize

impl<'q, T> Encode<'q, Postgres> for Option<T>

where T: Encode<'q, Postgres> + Type<Postgres> + 'q,

fn produces(&self) -> Option<<Postgres as Database>::TypeInfo>

fn encode( self, buf: &mut <Postgres as Database>::ArgumentBuffer<'q>, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

Writes the value of self into buf in the expected format for the database.

fn encode_by_ref( &self, buf: &mut <Postgres as Database>::ArgumentBuffer<'q>, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

Writes the value of self into buf without moving self.

fn size_hint(&self) -> usize

impl<'q, T> Encode<'q, Sqlite> for Option<T>

where T: Encode<'q, Sqlite> + Type<Sqlite> + 'q,

fn produces(&self) -> Option<<Sqlite as Database>::TypeInfo>

fn encode( self, buf: &mut <Sqlite as Database>::ArgumentBuffer<'q>, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

Writes the value of self into buf in the expected format for the database.

fn encode_by_ref( &self, buf: &mut <Sqlite as Database>::ArgumentBuffer<'q>, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

Writes the value of self into buf without moving self.

fn size_hint(&self) -> usize

impl<T> Encode for Option<T>

where T: Encode,

fn encode<E>(&self, encoder: &mut E) -> Result<(), EncodeError>

where E: Encoder,

Encode a given type.

impl<T> Encode for Option<T>

where T: Encode,

fn encoded_len(&self) -> Result<Length, Error>

Compute the length of this value in bytes when encoded as ASN.1 DER.

fn encode(&self, writer: &mut dyn Writer) -> Result<(), Error>

Encode this value as ASN.1 DER using the provided [Writer].

fn encode_to_slice<'a>(&self, buf: &'a mut [u8]) -> Result<&'a [u8], Error>

Encode this value to the provided byte slice, returning a sub-slice containing the encoded message.

fn encode_to_vec(&self, buf: &mut Vec<u8>) -> Result<Length, Error>

Encode this message as ASN.1 DER, appending it to the provided byte vector.

fn to_vec(&self) -> Result<Vec<u8>, Error>

Serialize this message as a byte vector.

impl<T> Encode for Option<T>

where T: Encode,

fn encoded_len(&self) -> Result<Length, Error>

Compute the length of this value in bytes when encoded as ASN.1 DER.

fn encode(&self, writer: &mut impl Writer) -> Result<(), Error>

Encode this value as ASN.1 DER using the provided [Writer].

fn encode_to_slice<'a>(&self, buf: &'a mut [u8]) -> Result<&'a [u8], Error>

Encode this value to the provided byte slice, returning a sub-slice containing the encoded message.

fn encode_to_vec(&self, buf: &mut Vec<u8>) -> Result<Length, Error>

Encode this message as ASN.1 DER, appending it to the provided byte vector.

fn to_der(&self) -> Result<Vec<u8>, Error>

Encode this type as DER, returning a byte vector.

impl<T> EstimateSize for Option<T>

where T: EstimateSize,

fn estimated_heap_size(&self) -> usize

The estimated heap size of the current struct in bytes.

fn estimated_size(&self) -> usize

where Self: Sized,

The estimated total size of the current struct in bytes, including the estimated_heap_size and the size of Self.

impl<T> From<Checked<T>> for Option<T>

fn from(checked: Checked<T>) -> Option<T>

Converts to this type from the input type.

impl<T> From<Checked<T>> for Option<T>

fn from(checked: Checked<T>) -> Option<T>

Converts to this type from the input type.

impl<T> From<CtOption<T>> for Option<T>

fn from(source: CtOption<T>) -> Option<T>

Convert the CtOption<T> wrapper into an Option<T>, depending on whether the underlying is_some Choice was a 0 or a 1 once unwrapped.

Note

This function exists to avoid ending up with ugly, verbose and/or bad handled conversions from the CtOption<T> wraps to an Option<T> or Result<T, E>. This implementation doesn’t intend to be constant-time nor try to protect the leakage of the T since the Option<T> will do it anyways.

impl<T> From<NotZero<T>> for Option<T>

where T: Zero,

fn from(not_zero: NotZero<T>) -> Option<T>

Converts to this type from the input type.

impl<T> From<OptionIr2<T>> for Option<T>

where T: FromValue,

fn from(ir: OptionIr2<T>) -> Option<T>

Converts to this type from the input type.

impl<T> From<T> for Option<T>

fn from(val: T) -> Option<T>

Moves val into a new Some.

Examples

let o: Option<u8> = Option::from(67);

assert_eq!(Some(67), o);

impl<A, V> FromIterator<Option<A>> for Option<V>

where V: FromIterator<A>,

fn 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.

impl<T, U> FromOptionalField<U> for Option<T>

where T: TryInto<U, Error = Error>,

fn optional(self) -> Result<Option<U>, Error>

Converts an optional protobuf field to an option of a different type

fn required(self, field: impl Into<String>) -> Result<U, Error>

Converts an optional protobuf field to a different type, returning an error if None

impl<T> FromRedisValue for Option<T>

where T: FromRedisValue,

fn from_redis_value(v: &Value) -> Result<Option<T>, RedisError>

Given a redis Value this attempts to convert it into the given destination type. If that fails because it’s not compatible an appropriate error is generated.

fn from_owned_redis_value(v: Value) -> Result<Option<T>, RedisError>

Given a redis Value this attempts to convert it into the given destination type. If that fails because it’s not compatible an appropriate error is generated.

fn from_redis_values(items: &[Value]) -> Result<Vec<Self>, RedisError>

Similar to from_redis_value but constructs a vector of objects from another vector of values. This primarily exists internally to customize the behavior for vectors of tuples.

fn from_owned_redis_values(items: Vec<Value>) -> Result<Vec<Self>, RedisError>

The same as from_redis_values, but takes a Vec<Value> instead of a &[Value].

fn from_byte_vec(_vec: &[u8]) -> Option<Vec<Self>>

Convert bytes to a single element vector.

fn from_owned_byte_vec(_vec: Vec<u8>) -> Result<Vec<Self>, RedisError>

Convert bytes to a single element vector.

impl<S, T> FromRequest<S> for Option<T>

where T: FromRequest<S>, S: Send + Sync,

type Rejection = Infallible

If the extractor fails it’ll use this “rejection” type. A rejection is a kind of error that can be converted into a response.

fn from_request<'life0, 'async_trait>( req: Request<Body>, state: &'life0 S, ) -> Pin<Box<dyn Future<Output = Result<Option<T>, <Option<T> as FromRequest<S>>::Rejection>> + Send + 'async_trait>>

where 'life0: 'async_trait, Option<T>: 'async_trait,

Perform the extraction.

impl<S, T> FromRequestParts<S> for Option<T>

where T: FromRequestParts<S>, S: Send + Sync,

type Rejection = Infallible

If the extractor fails it’ll use this “rejection” type. A rejection is a kind of error that can be converted into a response.

fn from_request_parts<'life0, 'life1, 'async_trait>( parts: &'life0 mut Parts, state: &'life1 S, ) -> Pin<Box<dyn Future<Output = Result<Option<T>, <Option<T> as FromRequestParts<S>>::Rejection>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, Option<T>: 'async_trait,

Perform the extraction.

impl<T> FromResidual<Option<Infallible>> for Option<T>

fn from_residual(residual: Option<Infallible>) -> Option<T>

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from a compatible Residual type.

impl<T> FromResidual<Yeet<()>> for Option<T>

fn from_residual(_: Yeet<()>) -> Option<T>

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from a compatible Residual type.

impl<'a, T> FromSql<'a> for Option<T>

where T: FromSql<'a>,

fn from_sql( ty: &Type, raw: &'a [u8], ) -> Result<Option<T>, Box<dyn Error + Send + Sync>>

Creates a new value of this type from a buffer of data of the specified Postgres Type in its binary format.

fn from_sql_null(_: &Type) -> Result<Option<T>, Box<dyn Error + Send + Sync>>

Creates a new value of this type from a NULL SQL value.

fn accepts(ty: &Type) -> bool

Determines if a value of this type can be created from the specified Postgres Type.

fn from_sql_nullable( ty: &Type, raw: Option<&'a [u8]>, ) -> Result<Self, Box<dyn Error + Send + Sync>>

A convenience function that delegates to from_sql and from_sql_null depending on the value of raw.

impl<T> FromValue for Option<T>

where T: FromValue,

type Intermediate = OptionIr2<T>

fn from_value(v: Value) -> Self

Will panic if could not convert v to Self.

fn from_value_opt(v: Value) -> Result<Self, FromValueError>

Will return Err(Error::FromValueError(v)) if could not convert v to Self.

fn get_intermediate(v: Value) -> Result<Self::Intermediate, FromValueError>

Will return Err(Error::FromValueError(v)) if v is not convertible to Self.

impl<T> Hash for Option<T>

where T: Hash,

fn hash<__H>(&self, state: &mut __H)

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<V> IntoActiveValue<Option<V>> for Option<V>

where V: IntoActiveValue<V> + Into<Value> + Nullable,

fn into_active_value(self) -> ActiveValue<Option<V>>

Method to perform the conversion

impl<T> IntoIterator for Option<T>

fn into_iter(self) -> IntoIter<T>

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 = T

The type of the elements being iterated over.

type IntoIter = IntoIter<T>

Which kind of iterator are we turning this into?

impl<T> IntoResponseParts for Option<T>

where T: IntoResponseParts,

type Error = <T as IntoResponseParts>::Error

The type returned in the event of an error.

fn into_response_parts( self, res: ResponseParts, ) -> Result<ResponseParts, <Option<T> as IntoResponseParts>::Error>

Set parts of the response

impl<T> IntoResult<T> for Option<T>

type Err = ParseError

fn into_result(self) -> Result<T, <Option<T> as IntoResult<T>>::Err>

impl<T> KnownLayout for Option<T>

type PointerMetadata = ()

The type of metadata stored in a pointer to Self.

impl<L, S> Layer<S> for Option<L>

where L: Layer<S>, S: Subscriber,

fn on_layer(&mut self, subscriber: &mut S)

Performs late initialization when attaching a Layer to a [Subscriber].

fn on_new_span(&self, attrs: &Attributes<'_>, id: &Id, ctx: Context<'_, S>)

Notifies this layer that a new span was constructed with the given Attributes and Id.

fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest

Registers a new callsite with this layer, returning whether or not the layer is interested in being notified about the callsite, similarly to Subscriber::register_callsite.

fn enabled(&self, metadata: &Metadata<'_>, ctx: Context<'_, S>) -> bool

Returns true if this layer is interested in a span or event with the given metadata in the current [Context], similarly to Subscriber::enabled.

fn on_record(&self, span: &Id, values: &Record<'_>, ctx: Context<'_, S>)

Notifies this layer that a span with the given Id recorded the given values.

fn on_follows_from(&self, span: &Id, follows: &Id, ctx: Context<'_, S>)

Notifies this layer that a span with the ID span recorded that it follows from the span with the ID follows.

fn event_enabled(&self, event: &Event<'_>, ctx: Context<'_, S>) -> bool

Called before on_event, to determine if on_event should be called.

fn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>)

Notifies this layer that an event has occurred.

fn on_enter(&self, id: &Id, ctx: Context<'_, S>)

Notifies this layer that a span with the given ID was entered.

fn on_exit(&self, id: &Id, ctx: Context<'_, S>)

Notifies this layer that the span with the given ID was exited.

fn on_close(&self, id: Id, ctx: Context<'_, S>)

Notifies this layer that the span with the given ID has been closed.

fn on_id_change(&self, old: &Id, new: &Id, ctx: Context<'_, S>)

Notifies this layer that a span ID has been cloned, and that the subscriber returned a different ID.

fn on_register_dispatch(&self, collector: &Dispatch)

Performs late initialization when installing this layer as a Subscriber.

fn and_then<L>(self, layer: L) -> Layered<L, Self, S>

where L: Layer<S>, Self: Sized,

Composes this layer around the given Layer, returning a Layered struct implementing Layer.

fn with_subscriber(self, inner: S) -> Layered<Self, S>

where Self: Sized,

Composes this Layer with the given Subscriber, returning a Layered struct that implements Subscriber.

fn with_filter<F>(self, filter: F) -> Filtered<Self, F, S>

where Self: Sized, F: Filter<S>,

Combines self with a [Filter], returning a Filtered layer.

fn boxed(self) -> Box<dyn Layer<S> + Send + Sync>

where Self: Sized + Layer<S> + Send + Sync + 'static, S: Subscriber,

Erases the type of this [Layer], returning a Boxed dyn Layer trait object.

impl<P> List for Option<P>

where P: List,

async fn next(&mut self) -> Result<Option<Entry>, Error>

Fetch a new page of [Entry]

impl<P> List for Option<P>

where P: List,

async fn next(&mut self) -> Result<Option<Entry>, Error>

Fetch a new page of [Entry]

impl<T> Monoid for Option<T>

where T: Semigroup + Clone,

fn empty() -> Option<T>

For a given Monoid, returns its empty/zero value

impl<T> OptionExt<T> for Option<T>

fn context<C, E>(self, context: C) -> Result<T, E>

where C: IntoError<E, Source = NoneError>, E: Error + ErrorCompat,

Convert an Option into a Result with additional context-sensitive information.

fn with_context<F, C, E>(self, context: F) -> Result<T, E>

where F: FnOnce() -> C, C: IntoError<E, Source = NoneError>, E: Error + ErrorCompat,

Convert an Option into a Result with lazily-generated context-sensitive information.

fn whatever_context<S, E>(self, context: S) -> Result<T, E>

where S: Into<String>, E: FromString,

Convert an Option into a Result with information from a string.

fn with_whatever_context<F, S, E>(self, context: F) -> Result<T, E>

where F: FnOnce() -> S, S: Into<String>, E: FromString,

Convert an Option into a Result with information from a lazily-generated string.

impl<T> OptionExt<T> for Option<T>

unsafe fn strict_unwrap_unchecked(self) -> T

Use unwrap_unchecked by default. Use unwrap when feature “strict_assertions” is enabled.

impl<T> OptionExt for Option<T>

type Val = T

Wrapped type by Option.

fn then<F>(self, f: F)

where F: FnOnce(<Option<T> as OptionExt>::Val),

Consume the wrapped value with the given function if there is.

impl<T> Ord for Option<T>

where T: Ord,

fn cmp(&self, other: &Option<T>) -> 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<T> OwnedToRef for Option<T>

where T: OwnedToRef,

type Borrowed<'a> = Option<<T as OwnedToRef>::Borrowed<'a>> where T: 'a

The resulting type referencing back to Self

fn owned_to_ref(&self) -> <Option<T> as OwnedToRef>::Borrowed<'_>

Creates a new object referencing back to the self for storage

impl<T> PartialEq for Option<T>

where T: PartialEq,

fn eq(&self, other: &Option<T>) -> 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<T> PartialOrd for Option<T>

where T: PartialOrd,

fn partial_cmp(&self, other: &Option<T>) -> 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<T> PgHasArrayType for Option<T>

where T: PgHasArrayType,

fn array_type_info() -> PgTypeInfo

fn array_compatible(ty: &PgTypeInfo) -> bool

impl<T> Predicate for Option<T>

where T: Predicate,

fn should_compress<B>(&self, response: &Response<B>) -> bool

where B: Body,

Should this response be compressed or not?

fn and<Other>(self, other: Other) -> And<Self, Other>

where Self: Sized, Other: Predicate,

Combine two predicates into one.

impl<T, U> Product<Option<U>> for Option<T>

where T: Product<U>,

fn 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.

Examples

This multiplies each number in a vector of strings, if a string could not be parsed the operation returns None:

let nums = vec!["5", "10", "1", "2"];
let total: Option<usize> = nums.iter().map(|w| w.parse::<usize>().ok()).product();
assert_eq!(total, Some(100));
let nums = vec!["5", "10", "one", "2"];
let total: Option<usize> = nums.iter().map(|w| w.parse::<usize>().ok()).product();
assert_eq!(total, None);

impl<T> RefCnt for Option<T>

where T: RefCnt,

type Base = <T as RefCnt>::Base

The base type the pointer points to.

fn into_ptr(me: Option<T>) -> *mut <T as RefCnt>::Base

Converts the smart pointer into a raw pointer, without affecting the reference count.

fn as_ptr(me: &Option<T>) -> *mut <T as RefCnt>::Base

Provides a view into the smart pointer as a raw pointer.

unsafe fn from_ptr(ptr: *const <T as RefCnt>::Base) -> Option<T>

Converts a raw pointer back into the smart pointer, without affecting the reference count.

fn inc(me: &Self) -> *mut Self::Base

Increments the reference count by one.

unsafe fn dec(ptr: *const Self::Base)

Decrements the reference count by one.

impl<'a, T> RefToOwned<'a> for Option<T>

where T: RefToOwned<'a> + 'a, <T as RefToOwned<'a>>::Owned: OwnedToRef,

type Owned = Option<<T as RefToOwned<'a>>::Owned>

The resulting type after obtaining ownership.

fn ref_to_owned(&self) -> <Option<T> as RefToOwned<'a>>::Owned

Creates a new object taking ownership of the data

impl<R> Row for Option<R>

where R: Row,

Implements Row for an optional row.

fn datum_at(&self, index: usize) -> Option<ScalarRefImpl<'_>>

Returns the DatumRef at the given index.

unsafe fn datum_at_unchecked(&self, index: usize) -> Option<ScalarRefImpl<'_>>

Returns the DatumRef at the given index without bounds checking.

fn len(&self) -> usize

Returns the number of datum in the row.

fn iter(&self) -> impl Iterator<Item = Option<ScalarRefImpl<'_>>>

Returns an iterator over the datums in the row, in DatumRef form.

fn to_owned_row(&self) -> OwnedRow

Converts the row into an OwnedRow.

fn into_owned_row(self) -> OwnedRow

Consumes self and converts it into an OwnedRow.

fn value_serialize_into(&self, buf: impl BufMut)

Serializes the row with value encoding, into the given buf.

fn memcmp_serialize_into(&self, serde: &OrderedRowSerde, buf: impl BufMut)

Serializes the row with memcomparable encoding, into the given buf. As each datum may have different order type, a serde should be provided.

fn is_empty(&self) -> bool

Returns true if the row contains no datum.

fn value_serialize(&self) -> Vec<u8>

Serializes the row with value encoding and returns the bytes.

fn value_serialize_bytes(&self) -> Bytes

Serializes the row with value encoding and returns the bytes.

fn value_estimate_size(&self) -> usize

fn memcmp_serialize(&self, serde: &OrderedRowSerde) -> Vec<u8>

Serializes the row with memcomparable encoding and return the bytes. As each datum may have different order type, a serde should be provided.

fn hash_datums_into<H>(&self, state: &mut H)

where H: Hasher,

Hash the datums of this row into the given hasher.

fn hash<H>(&self, hash_builder: H) -> HashCode<H>

where H: BuildHasher,

Returns the hash code of the row.

fn eq(this: &Self, other: impl Row) -> bool

Determines whether the datums of this row are equal to those of another.

impl<T> Semigroup for Option<T>

where T: Semigroup + Clone,

fn combine(&self, other: &Option<T>) -> Option<T>

Associative operation taking which combines two values.

impl<T> Serialize for Option<T>

where T: Serialize,

fn serialize<S>( &self, serializer: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl<T> Serialize for Option<T>

where T: Serialize,

fn serialize<S>( &self, serializer: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

impl<T, U> SerializeAs<Option<T>> for Option<U>

where U: SerializeAs<T>,

fn serialize_as<S>( source: &Option<T>, serializer: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl<S> Source for Option<S>

where S: Source,

fn visit<'kvs>( &'kvs self, visitor: &mut dyn VisitSource<'kvs>, ) -> Result<(), Error>

Visit key-values.

fn get(&self, key: Key<'_>) -> Option<Value<'_>>

Get the value for a given key.

fn count(&self) -> usize

Count the number of key-values that can be visited.

impl<T, U> Sum<Option<U>> for Option<T>

where T: Sum<U>,

fn 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));
let words = vec!["have", "a", "good", "day"];
let total: Option<usize> = words.iter().map(|w| w.find('a')).sum();
assert_eq!(total, None);

impl<T> TapOptional for Option<T>

type Val = T

The interior type that the container may or may not carry.

fn tap_some(self, func: impl FnOnce(&T)) -> Option<T>

Immutabily accesses an interior value only when it is present.

fn tap_some_mut(self, func: impl FnOnce(&mut T)) -> Option<T>

Mutably accesses an interor value only when it is present.

fn tap_none(self, func: impl FnOnce()) -> Option<T>

Runs an effect function when the container is empty.

fn tap_some_dbg(self, func: impl FnOnce(&Self::Val)) -> Self

Calls .tap_some() only in debug builds, and is erased in release builds.

fn tap_some_mut_dbg(self, func: impl FnOnce(&mut Self::Val)) -> Self

Calls .tap_some_mut() only in debug builds, and is erased in release builds.

fn tap_none_dbg(self, func: impl FnOnce()) -> Self

Calls .tap_none() only in debug builds, and is erased in release builds.

impl ToDatumRef for Option<ScalarImpl>

fn to_datum_ref(&self) -> Option<ScalarRefImpl<'_>>

Convert the datum to DatumRef.

impl<T> ToOwnedDatum for Option<T>

where T: Into<ScalarImpl>,

fn to_owned_datum(self) -> Option<ScalarImpl>

Convert the datum to an owned Datum.

impl<T> ToRedisArgs for Option<T>

where T: ToRedisArgs,

fn write_redis_args<W>(&self, out: &mut W)

where W: RedisWrite + ?Sized,

This writes the value into a vector of bytes. Each item is a single argument. Most items generate a single item.

fn describe_numeric_behavior(&self) -> NumericBehavior

Returns an information about the contained value with regards to it’s numeric behavior in a redis context. This is used in some high level concepts to switch between different implementations of redis functions (for instance INCR vs INCRBYFLOAT).

fn num_of_args(&self) -> usize

Returns the number of arguments this value will generate.

fn to_redis_args(&self) -> Vec<Vec<u8>>

This converts the value into a vector of bytes. Each item is a single argument. Most items generate a vector of a single item.

impl<T> ToSql for Option<T>

where T: ToSql,

fn to_sql( &self, ty: &Type, out: &mut BytesMut, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

Converts the value of self into the binary format of the specified Postgres Type, appending it to out.

fn accepts(ty: &Type) -> bool

Determines if a value of this type can be converted to the specified Postgres Type.

fn encode_format(&self, ty: &Type) -> Format

Specify the encode format

fn to_sql_checked( &self, ty: &Type, out: &mut BytesMut, ) -> Result<IsNull, Box<dyn Error + Send + Sync>>

An adaptor method used internally by Rust-Postgres.

impl<T> ToValue for Option<T>

where T: ToValue,

fn to_value(&self) -> Value<'_>

Perform the conversion.

impl<T> Try for Option<T>

type Output = T

🔬This is a nightly-only experimental API. (try_trait_v2)

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)

The type of the value passed to FromResidual::from_residual as part of ? when short-circuiting.

fn from_output(output: <Option<T> as Try>::Output) -> Option<T>

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from its Output type.

fn branch( self, ) -> ControlFlow<<Option<T> as Try>::Residual, <Option<T> as Try>::Output>

🔬This is a nightly-only experimental API. (try_trait_v2)

Used in ? to decide whether the operator should produce a value (because this returned ControlFlow::Continue) or propagate a value back to the caller (because this returned ControlFlow::Break).

impl<T> TryGetable for Option<T>

where T: TryGetable,

fn try_get_by<I>(res: &QueryResult, index: I) -> Result<Option<T>, TryGetError>

where I: ColIdx,

Get a value from the query result with an ColIdx

fn try_get(res: &QueryResult, pre: &str, col: &str) -> Result<Self, TryGetError>

Get a value from the query result with prefixed column name

fn try_get_by_index( res: &QueryResult, index: usize, ) -> Result<Self, TryGetError>

Get a value from the query result based on the order in the select expressions

impl<T, DB> Type<DB> for Option<T>

where T: Type<DB>, DB: Database,

fn type_info() -> <DB as Database>::TypeInfo

Returns the canonical SQL type for this Rust type.

fn compatible(ty: &<DB as Database>::TypeInfo) -> bool

Determines if this Rust type is compatible with the given SQL type.

impl<V> TypedValue for Option<V>

where V: TypedValue,

fn value_type(&self) -> ValueType

Gets the type of the current value

impl<T> Value for Option<T>

where T: Value,

fn record(&self, key: &Field, visitor: &mut dyn Visit)

Visits this value with the given Visitor.

impl<V> ValueAsArray for Option<V>

where V: ValueAsArray,

type Array = <V as ValueAsArray>::Array

The array structure

fn as_array(&self) -> Option<&<Option<V> as ValueAsArray>::Array>

Tries to represent the value as an array and returns a reference to it

impl<V> ValueAsObject for Option<V>

where V: ValueAsObject,

type Object = <V as ValueAsObject>::Object

The object structure

fn as_object(&self) -> Option<&<Option<V> as ValueAsObject>::Object>

Tries to represent the value as an object and returns a reference to it

impl<V> ValueAsScalar for Option<V>

where V: ValueAsScalar,

fn as_null(&self) -> Option<()>

Tries to represent the value as a ‘null’;

fn as_bool(&self) -> Option<bool>

Tries to represent the value as a bool

fn as_i64(&self) -> Option<i64>

Tries to represent the value as an i64

fn as_u64(&self) -> Option<u64>

Tries to represent the value as an u64

fn as_f64(&self) -> Option<f64>

Tries to represent the value as a f64

fn as_str(&self) -> Option<&str>

Tries to represent the value as a &str

fn as_i128(&self) -> Option<i128>

Tries to represent the value as an i128

fn as_i32(&self) -> Option<i32>

Tries to represent the value as an i32

fn as_i16(&self) -> Option<i16>

Tries to represent the value as an i16

fn as_i8(&self) -> Option<i8>

Tries to represent the value as an i8

fn as_u128(&self) -> Option<u128>

Tries to represent the value as an u128

fn as_usize(&self) -> Option<usize>

Tries to represent the value as an usize

fn as_u32(&self) -> Option<u32>

Tries to represent the value as an u32

fn as_u16(&self) -> Option<u16>

Tries to represent the value as an u16

fn as_u8(&self) -> Option<u8>

Tries to represent the value as an u8

fn as_f32(&self) -> Option<f32>

Tries to represent the value as a f32

fn cast_f64(&self) -> Option<f64>

Casts the current value to a f64 if possible, this will turn integer values into floats.

fn as_char(&self) -> Option<char>

Tries to represent the value as a Char

impl<V> ValueIntoArray for Option<V>

where V: ValueIntoArray,

type Array = <V as ValueIntoArray>::Array

The type for Arrays

fn into_array(self) -> Option<<Option<V> as ValueIntoArray>::Array>

Tries to turn the value into it’s array representation

impl<V> ValueIntoObject for Option<V>

where V: ValueIntoObject,

type Object = <V as ValueIntoObject>::Object

The type for Objects

fn into_object(self) -> Option<<Option<V> as ValueIntoObject>::Object>

Tries to turn the value into it’s object representation

impl<V> ValueIntoString for Option<V>

where V: ValueIntoString,

type String = <V as ValueIntoString>::String

The type for Strings

fn into_string(self) -> Option<<Option<V> as ValueIntoString>::String>

Tries to turn the value into it’s string representation

impl<T> ValueType for Option<T>

where T: ValueType + Nullable,

fn try_from(v: Value) -> Result<Option<T>, ValueTypeErr>

fn type_name() -> String

fn array_type() -> ArrayType

fn column_type() -> ColumnType

fn unwrap(v: Value) -> Self

fn expect(v: Value, msg: &str) -> Self

impl<T> Visit for Option<T>

where T: Visit,

fn visit<V>(&self, visitor: &mut V) -> ControlFlow<<V as Visitor>::Break>

where V: Visitor,

impl<T> VisitMut for Option<T>

where T: VisitMut,

fn visit<V>(&mut self, visitor: &mut V) -> ControlFlow<<V as VisitorMut>::Break>

where V: VisitorMut,

impl<T> WithDataType for Option<T>

where T: WithDataType,

fn default_data_type() -> DataType

Returns the most obvious DataType for the rust type.

impl<T> Zeroable for Option<T>

where T: ZeroableInOption,

fn zeroed() -> Self

Calls zeroed.

impl<Z> Zeroize for Option<Z>

where Z: Zeroize,

fn zeroize(&mut self)

Zero out this object from memory using Rust intrinsics which ensure the zeroization operation is not “optimized away” by the compiler.

impl<T> Copy for Option<T>

where T: Copy,

impl<T> Eq for Option<T>

where T: Eq,

impl<T> Immutable for Option<T>

where T: Immutable,

impl<T> Nullable for Option<T>

impl<T> Pod for Option<T>

where T: PodInOption,

impl<T> StructuralPartialEq for Option<T>

impl<Z> ZeroizeOnDrop for Option<Z>

where Z: ZeroizeOnDrop,