Struct Locale

pub struct Locale {
    pub id: LanguageIdentifier,
    pub extensions: Extensions,
}

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:

1. A string ordering, suitable for stable serialization: Locale::strict_cmp
2. 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

pub const UNKNOWN: Self

The unknown locale “und”.

pub fn strict_cmp(&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);

pub fn total_cmp(&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

pub fn to_string(&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.

Trait Implementations

impl Clone for Locale

fn clone(&self) -> Locale

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Locale

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

Formats the value using the given formatter.

impl Display for Locale

This trait is implemented for compatibility with fmt!. To create a string, [Writeable::write_to_string] is usually more efficient.

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

Formats the value using the given formatter.

impl From<&Locale> for DataLocale

fn from(locale: &Locale) -> Self

Converts to this type from the input type.

impl From<&Locale> for LocalePreferences

fn from(loc: &Locale) -> Self

Converts to this type from the input type.

impl From<(Language, Option<Script>, Option<Region>)> for Locale

Examples

use icu::locale::Locale;
use icu::locale::{
    locale,
    subtags::{language, region, script},
};

assert_eq!(
    Locale::from((
        language!("en"),
        Some(script!("Latn")),
        Some(region!("US"))
    )),
    locale!("en-Latn-US")
);

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

Converts to this type from the input type.

impl From<Language> for Locale

Examples

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

assert_eq!(Locale::from(language!("en")), locale!("en"));

fn from(language: Language) -> Self

Converts to this type from the input type.

impl From<LanguageIdentifier> for Locale

fn from(id: LanguageIdentifier) -> Self

Converts to this type from the input type.

impl From<Locale> for DataLocale

fn from(locale: Locale) -> Self

Converts to this type from the input type.

impl From<Locale> for LanguageIdentifier

fn from(loc: Locale) -> Self

Converts to this type from the input type.

impl From<Option<Region>> for Locale

Examples

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

assert_eq!(Locale::from(Some(region!("US"))), locale!("und-US"));

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

Converts to this type from the input type.

impl From<Option<Script>> for Locale

Examples

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

assert_eq!(Locale::from(Some(script!("latn"))), locale!("und-Latn"));

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

Converts to this type from the input type.

impl Hash for Locale

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

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 PartialEq for Locale

fn eq(&self, other: &Locale) -> 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 Writeable for Locale

fn write_to<W: Write + ?Sized>(&self, sink: &mut W) -> Result

Writes a string to the given sink. Errors from the sink are bubbled up. The default implementation delegates to write_to_parts, and discards any Part annotations.

fn writeable_length_hint(&self) -> LengthHint

Returns a hint for the number of UTF-8 bytes that will be written to the sink.

fn write_to_parts<S>(&self, sink: &mut S) -> Result<(), Error>

where S: PartsWrite + ?Sized,

Write bytes and Part annotations to the given sink. Errors from the sink are bubbled up. The default implementation delegates to write_to, and doesn’t produce any Part annotations.

fn write_to_string(&self) -> Cow<'_, str>

Creates a new String with the data from this Writeable. Like ToString, but smaller and faster.

impl Eq for Locale

impl StructuralPartialEq for Locale