Struct `Locale`

struct Locale { ... }

A core struct representing a Unicode Locale Identifier.

A locale is made of two parts:

Unicode Language Identifier
A set of Unicode Extensions

Locale exposes all of the same fields and methods as LanguageIdentifier, and on top of that is able to parse, manipulate and serialize unicode extension fields.

Ordering

This type deliberately does not implement Ord or PartialOrd because there are multiple possible orderings. Depending on your use case, two orderings are available:

A string ordering, suitable for stable serialization: Locale::strict_cmp
A struct ordering, suitable for use with a BTreeSet: Locale::total_cmp

See issue: https://github.com/unicode-org/icu4x/issues/1215

Parsing

Unicode recognizes three levels of standard conformance for a locale:

well-formed - syntactically correct
valid - well-formed and only uses registered language subtags, extensions, keywords, types...
canonical - valid and no deprecated codes or structure.

Any syntactically invalid subtags will cause the parsing to fail with an error.

This operation normalizes syntax to be well-formed. No legacy subtag replacements is performed. For validation and canonicalization, see LocaleCanonicalizer.

ICU4X's Locale parsing does not allow for non-BCP-47-compatible locales allowed by UTS 35 for backwards compatability. Furthermore, it currently does not allow for language tags to have more than three characters.

Examples

Simple example:

use icu::locale::{
    extensions::unicode::{key, value},
    locale,
    subtags::{language, region},
};

let loc = locale!("en-US-u-ca-buddhist");

assert_eq!(loc.id.language, language!("en"));
assert_eq!(loc.id.script, None);
assert_eq!(loc.id.region, Some(region!("US")));
assert_eq!(loc.id.variants.len(), 0);
assert_eq!(
    loc.extensions.unicode.keywords.get(&key!("ca")),
    Some(&value!("buddhist"))
);

More complex example:

use icu::locale::{subtags::*, Locale};

let loc: Locale = "eN-latn-Us-Valencia-u-hC-H12"
    .parse()
    .expect("Failed to parse.");

assert_eq!(loc.id.language, "en".parse::<Language>().unwrap());
assert_eq!(loc.id.script, "Latn".parse::<Script>().ok());
assert_eq!(loc.id.region, "US".parse::<Region>().ok());
assert_eq!(
    loc.id.variants.get(0),
    "valencia".parse::<Variant>().ok().as_ref()
);

Fields

id: LanguageIdentifier: The basic language/script/region components in the locale identifier along with any variants.
extensions: Extensions: Any extensions present in the locale identifier.

Implementations

`impl Locale`

fn strict_cmp(self: &Self, other: &[u8]) -> Ordering

Compare this Locale with BCP-47 bytes.

The return value is equivalent to what would happen if you first converted this Locale to a BCP-47 string and then performed a byte comparison.

This function is case-sensitive and results in a total order, so it is appropriate for binary search. The only argument producing Ordering::Equal is self.to_string().

Examples

Sorting a list of locales with this method requires converting one of them to a string:

use icu::locale::Locale;
use std::cmp::Ordering;
use writeable::Writeable;

// Random input order:
let bcp47_strings: &[&str] = &[
    "und-u-ca-hebrew",
    "ar-Latn",
    "zh-Hant-TW",
    "zh-TW",
    "und-fonipa",
    "zh-Hant",
    "ar-SA",
];

let mut locales = bcp47_strings
    .iter()
    .map(|s| s.parse().unwrap())
    .collect::<Vec<Locale>>();
locales.sort_by(|a, b| {
    let b = b.write_to_string();
    a.strict_cmp(b.as_bytes())
});
let strict_cmp_strings = locales
    .iter()
    .map(|l| l.to_string())
    .collect::<Vec<String>>();

// Output ordering, sorted alphabetically
let expected_ordering: &[&str] = &[
    "ar-Latn",
    "ar-SA",
    "und-fonipa",
    "und-u-ca-hebrew",
    "zh-Hant",
    "zh-Hant-TW",
    "zh-TW",
];

assert_eq!(expected_ordering, strict_cmp_strings);

fn total_cmp(self: &Self, other: &Self) -> Ordering

Returns an ordering suitable for use in BTreeSet.

Unlike Locale::strict_cmp, the ordering may or may not be equivalent to string ordering, and it may or may not be stable across ICU4X releases.

Examples

This method returns a nonsensical ordering derived from the fields of the struct:

use icu::locale::Locale;
use std::cmp::Ordering;

// Input strings, sorted alphabetically
let bcp47_strings: &[&str] = &[
    "ar-Latn",
    "ar-SA",
    "und-fonipa",
    "und-u-ca-hebrew",
    "zh-Hant",
    "zh-Hant-TW",
    "zh-TW",
];
assert!(bcp47_strings.windows(2).all(|w| w[0] < w[1]));

let mut locales = bcp47_strings
    .iter()
    .map(|s| s.parse().unwrap())
    .collect::<Vec<Locale>>();
locales.sort_by(Locale::total_cmp);
let total_cmp_strings = locales
    .iter()
    .map(|l| l.to_string())
    .collect::<Vec<String>>();

// Output ordering, sorted arbitrarily
let expected_ordering: &[&str] = &[
    "ar-SA",
    "ar-Latn",
    "und-u-ca-hebrew",
    "und-fonipa",
    "zh-TW",
    "zh-Hant",
    "zh-Hant-TW",
];

assert_eq!(expected_ordering, total_cmp_strings);

Use a wrapper to add a Locale to a BTreeSet:

use icu::locale::Locale;
use std::cmp::Ordering;
use std::collections::BTreeSet;

#[derive(PartialEq, Eq)]
struct LocaleTotalOrd(Locale);

impl Ord for LocaleTotalOrd {
    fn cmp(&self, other: &Self) -> Ordering {
        self.0.total_cmp(&other.0)
    }
}

impl PartialOrd for LocaleTotalOrd {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

let _: BTreeSet<LocaleTotalOrd> = unimplemented!();

`impl Locale`

fn to_string(self: &Self) -> String

Converts the given value to a String.

Under the hood, this uses an efficient Writeable implementation. However, in order to avoid allocating a string, it is more efficient to use Writeable directly.

`impl Clone for Locale`

fn clone(self: &Self) -> Locale

`impl Debug for Locale`

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

`impl Display for Locale`

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

`impl Eq for Locale`

`impl Freeze for Locale`

`impl From for Locale`

fn from(lsr: (Language, Option<Script>, Option<Region>)) -> Self

`impl From for Locale`

fn from(region: Option<Region>) -> Self

`impl From for Locale`

fn from(id: LanguageIdentifier) -> Self

`impl From for Locale`

fn from(script: Option<Script>) -> Self

`impl From for Locale`

fn from(language: Language) -> Self

`impl Hash for Locale`

fn hash<__H: $crate::hash::Hasher>(self: &Self, state: &mut __H)

`impl PartialEq for Locale`

fn eq(self: &Self, other: &Locale) -> bool

`impl RefUnwindSafe for Locale`

`impl Send for Locale`

`impl StructuralPartialEq for Locale`

`impl Sync for Locale`

`impl Unpin for Locale`

`impl UnsafeUnpin for Locale`

`impl UnwindSafe for Locale`

`impl Writeable for Locale`

fn write_to<W: core::fmt::Write + ?Sized>(self: &Self, sink: &mut W) -> Result
fn writeable_length_hint(self: &Self) -> LengthHint

`impl<T> Any for Locale`

fn type_id(self: &Self) -> TypeId

`impl<T> Borrow for Locale`

fn borrow(self: &Self) -> &T

`impl<T> BorrowMut for Locale`

fn borrow_mut(self: &mut Self) -> &mut T

`impl<T> CloneToUninit for Locale`

unsafe fn clone_to_uninit(self: &Self, dest: *mut u8)

`impl<T> ErasedDestructor for Locale`

`impl<T> From for Locale`

fn from(t: T) -> T: Returns the argument unchanged.

`impl<T> ToOwned for Locale`

fn to_owned(self: &Self) -> T
fn clone_into(self: &Self, target: &mut T)

`impl<T> ToString for Locale`

fn to_string(self: &Self) -> String

`impl<T, U> Into for Locale`

fn into(self: Self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of [From]<T> for U chooses to do.

`impl<T, U> TryFrom for Locale`

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

`impl<T, U> TryInto for Locale`

fn try_into(self: Self) -> Result<U, <U as TryFrom<T>>::Error>