Struct fluent_bundle::bundle::FluentBundle

pub struct FluentBundle<R, M> {
    pub locales: Vec<LanguageIdentifier>,
    // some fields omitted
}

A collection of localization messages for a single locale, which are meant to be used together in a single view, widget or any other UI abstraction.

Examples

use fluent_bundle::{FluentBundle, FluentResource, FluentValue, FluentArgs};
use unic_langid::langid;

// 1. Create a FluentResource

let ftl_string = String::from("intro = Welcome, { $name }.");
let resource = FluentResource::try_new(ftl_string)
    .expect("Could not parse an FTL string.");


// 2. Create a FluentBundle

let langid_en = langid!("en-US");
let mut bundle = FluentBundle::new(vec![langid_en]);


// 3. Add the resource to the bundle

bundle.add_resource(&resource)
    .expect("Failed to add FTL resources to the bundle.");


// 4. Retrieve a FluentMessage from the bundle

let msg = bundle.get_message("intro")
    .expect("Message doesn't exist.");

let mut args = FluentArgs::new();
args.set("name", "Rustacean");


// 5. Format the value of the message

let mut errors = vec![];

let pattern = msg.value()
    .expect("Message has no value.");

assert_eq!(
    bundle.format_pattern(&pattern, Some(&args), &mut errors),
    // The placeholder is wrapper in Unicode Directionality Marks
    // to indicate that the placeholder may be of different direction
    // than surrounding string.
    "Welcome, \u{2068}Rustacean\u{2069}."
);

FluentBundle Life Cycle

Create a bundle

To create a bundle, call FluentBundle::new with a locale list that represents the best possible fallback chain for a given locale. The simplest case is a one-locale list.

Fluent uses LanguageIdentifier which can be created using langid! macro.

Add Resources

Next, call add_resource one or more times, supplying translations in the FTL syntax.

Since FluentBundle is generic over anything that can borrow a FluentResource, one can use FluentBundle to own its resources, store references to them, or even Rc<FluentResource> or Arc<FluentResource>.

The FluentBundle instance is now ready to be used for localization.

Format

To format a translation, call get_message to retrieve a FluentMessage, and then call format_pattern on the message value or attribute in order to retrieve the translated string.

The result of format_pattern is an Cow<str>. It is recommended to treat the result as opaque from the perspective of the program and use it only to display localized messages. Do not examine it or alter in any way before displaying. This is a general good practice as far as all internationalization operations are concerned.

If errors were encountered during formatting, they will be accumulated in the Vec<FluentError> passed as the third argument.

While they are not fatal, they usually indicate problems with the translation, and should be logged or reported in a way that allows the developer to notice and fix them.

Locale Fallback Chain

FluentBundle stores messages in a single locale, but keeps a locale fallback chain for the purpose of language negotiation with i18n formatters. For instance, if date and time formatting are not available in the first locale, FluentBundle will use its locales fallback chain to negotiate a sensible fallback for date and time formatting.

Concurrency

As you may have noticed, fluent_bundle::FluentBundle is a specialization of fluent_bundle::bundle::FluentBundle which works with an IntlLangMemoizer over RefCell. In scenarios where the memoizer must work concurrently, there’s an implementation of IntlLangMemoizer that uses Mutex and there’s FluentBundle::new_concurrent which works with that.

Fields

locales: Vec<LanguageIdentifier>

Implementations

impl<R, M> FluentBundle<R, M>

pub fn add_resource(&mut self, r: R) -> Result<(), Vec<FluentError>> where
    R: Borrow<FluentResource>, 

Adds a resource to the bundle, returning an empty Result<T> on success.

If any entry in the resource uses the same identifier as an already existing key in the bundle, the new entry will be ignored and a FluentError::Overriding will be added to the result.

The method can take any type that can be borrowed to FluentResource:

• FluentResource
• &FluentResource
• Rc
• Arc

This allows the user to introduce custom resource management and share resources between instances of FluentBundle.

Examples

use fluent_bundle::{FluentBundle, FluentResource};
use unic_langid::langid;

let ftl_string = String::from("
hello = Hi!
goodbye = Bye!
");
let resource = FluentResource::try_new(ftl_string)
    .expect("Could not parse an FTL string.");
let langid_en = langid!("en-US");
let mut bundle = FluentBundle::new(vec![langid_en]);
bundle.add_resource(resource)
    .expect("Failed to add FTL resources to the bundle.");
assert_eq!(true, bundle.has_message("hello"));

Whitespace

Message ids must have no leading whitespace. Message values that span multiple lines must have leading whitespace on all but the first line. These are standard FTL syntax rules that may prove a bit troublesome in source code formatting. The indoc! crate can help with stripping extra indentation if you wish to indent your entire message.

pub fn add_resource_overriding(&mut self, r: R) where
    R: Borrow<FluentResource>, 

Adds a resource to the bundle, returning an empty Result<T> on success.

If any entry in the resource uses the same identifier as an already existing key in the bundle, the entry will override the previous one.

The method can take any type that can be borrowed as FluentResource:

• FluentResource
• &FluentResource
• Rc
• Arc

This allows the user to introduce custom resource management and share resources between instances of FluentBundle.

Examples

use fluent_bundle::{FluentBundle, FluentResource};
use unic_langid::langid;

let ftl_string = String::from("
hello = Hi!
goodbye = Bye!
");
let resource = FluentResource::try_new(ftl_string)
    .expect("Could not parse an FTL string.");

let ftl_string = String::from("
hello = Another Hi!
");
let resource2 = FluentResource::try_new(ftl_string)
    .expect("Could not parse an FTL string.");

let langid_en = langid!("en-US");

let mut bundle = FluentBundle::new(vec![langid_en]);
bundle.add_resource(resource)
    .expect("Failed to add FTL resources to the bundle.");

bundle.add_resource_overriding(resource2);

let mut errors = vec![];
let msg = bundle.get_message("hello")
    .expect("Failed to retrieve the message");
let value = msg.value().expect("Failed to retrieve the value of the message");
assert_eq!(bundle.format_pattern(value, None, &mut errors), "Another Hi!");

Whitespace

Message ids must have no leading whitespace. Message values that span multiple lines must have leading whitespace on all but the first line. These are standard FTL syntax rules that may prove a bit troublesome in source code formatting. The indoc! crate can help with stripping extra indentation if you wish to indent your entire message.

pub fn set_use_isolating(&mut self, value: bool)

When formatting patterns, FluentBundle inserts Unicode Directionality Isolation Marks to indicate that the direction of a placeable may differ from the surrounding message.

This is important for cases such as when a right-to-left user name is presented in the left-to-right message.

In some cases, such as testing, the user may want to disable the isolating.

pub fn set_transform(&mut self, func: Option<fn(_: &str) -> Cow<'_, str>>)

This method allows to specify a function that will be called on all textual fragments of the pattern during formatting.

This is currently primarly used for pseudolocalization, and fluent-pseudo crate provides a function that can be passed here.

pub fn set_formatter(
    &mut self,
    func: Option<fn(_: &FluentValue<'_>, _: &M) -> Option<String>>
)

This method allows to specify a function that will be called before any FluentValue is formatted allowing overrides.

It’s particularly useful for plugging in an external formatter for FluentValue::Number.

pub fn has_message(&self, id: &str) -> bool where
    R: Borrow<FluentResource>, 

Returns true if this bundle contains a message with the given id.

Examples

use fluent_bundle::{FluentBundle, FluentResource};
use unic_langid::langid;

let ftl_string = String::from("hello = Hi!");
let resource = FluentResource::try_new(ftl_string)
    .expect("Failed to parse an FTL string.");
let langid_en = langid!("en-US");
let mut bundle = FluentBundle::new(vec![langid_en]);
bundle.add_resource(&resource)
    .expect("Failed to add FTL resources to the bundle.");
assert_eq!(true, bundle.has_message("hello"));

pub fn get_message<'l>(&'l self, id: &str) -> Option<FluentMessage<'l>> where
    R: Borrow<FluentResource>, 

Retrieves a FluentMessage from a bundle.

Examples

use fluent_bundle::{FluentBundle, FluentResource};
use unic_langid::langid;

let ftl_string = String::from("hello-world = Hello World!");
let resource = FluentResource::try_new(ftl_string)
    .expect("Failed to parse an FTL string.");

let langid_en = langid!("en-US");
let mut bundle = FluentBundle::new(vec![langid_en]);

bundle.add_resource(&resource)
    .expect("Failed to add FTL resources to the bundle.");

let msg = bundle.get_message("hello-world");
assert_eq!(msg.is_some(), true);

pub fn write_pattern<'bundle, W>(
    &'bundle self,
    w: &mut W,
    pattern: &'bundle Pattern<&str>,
    args: Option<&'bundle FluentArgs<'_>>,
    errors: &mut Vec<FluentError>
) -> Result where
    R: Borrow<FluentResource>,
    W: Write,
    M: MemoizerKind, 

Writes a formatted pattern which comes from a FluentMessage.

Example

use fluent_bundle::{FluentBundle, FluentResource};
use unic_langid::langid;

let ftl_string = String::from("hello-world = Hello World!");
let resource = FluentResource::try_new(ftl_string)
    .expect("Failed to parse an FTL string.");

let langid_en = langid!("en-US");
let mut bundle = FluentBundle::new(vec![langid_en]);

bundle.add_resource(&resource)
    .expect("Failed to add FTL resources to the bundle.");

let msg = bundle.get_message("hello-world")
    .expect("Failed to retrieve a FluentMessage.");

let pattern = msg.value()
    .expect("Missing Value.");
let mut errors = vec![];

let mut s = String::new();
bundle.write_pattern(&mut s, &pattern, None, &mut errors)
    .expect("Failed to write.");

assert_eq!(s, "Hello World!");

pub fn format_pattern<'bundle>(
    &'bundle self,
    pattern: &'bundle Pattern<&str>,
    args: Option<&'bundle FluentArgs<'_>>,
    errors: &mut Vec<FluentError>
) -> Cow<'bundle, str> where
    R: Borrow<FluentResource>,
    M: MemoizerKind, 

Formats a pattern which comes from a FluentMessage.

Example

use fluent_bundle::{FluentBundle, FluentResource};
use unic_langid::langid;

let ftl_string = String::from("hello-world = Hello World!");
let resource = FluentResource::try_new(ftl_string)
    .expect("Failed to parse an FTL string.");

let langid_en = langid!("en-US");
let mut bundle = FluentBundle::new(vec![langid_en]);

bundle.add_resource(&resource)
    .expect("Failed to add FTL resources to the bundle.");

let msg = bundle.get_message("hello-world")
    .expect("Failed to retrieve a FluentMessage.");

let pattern = msg.value()
    .expect("Missing Value.");
let mut errors = vec![];

let result = bundle.format_pattern(&pattern, None, &mut errors);

assert_eq!(result, "Hello World!");

pub fn add_function<F>(&mut self, id: &str, func: F) -> Result<(), FluentError> where
    F: for<'a> Fn(&[FluentValue<'a>], &FluentArgs<'_>) -> FluentValue<'a> + Sync + Send + 'static, 

Makes the provided rust function available to messages with the name id. See the FTL syntax guide to learn how these are used in messages.

FTL functions accept both positional and named args. The rust function you provide therefore has two parameters: a slice of values for the positional args, and a FluentArgs for named args.

Examples

use fluent_bundle::{FluentBundle, FluentResource, FluentValue};
use unic_langid::langid;

let ftl_string = String::from("length = { STRLEN(\"12345\") }");
let resource = FluentResource::try_new(ftl_string)
    .expect("Could not parse an FTL string.");
let langid_en = langid!("en-US");
let mut bundle = FluentBundle::new(vec![langid_en]);
bundle.add_resource(&resource)
    .expect("Failed to add FTL resources to the bundle.");

// Register a fn that maps from string to string length
bundle.add_function("STRLEN", |positional, _named| match positional {
    [FluentValue::String(str)] => str.len().into(),
    _ => FluentValue::Error,
}).expect("Failed to add a function to the bundle.");

let msg = bundle.get_message("length").expect("Message doesn't exist.");
let mut errors = vec![];
let pattern = msg.value().expect("Message has no value.");
let value = bundle.format_pattern(&pattern, None, &mut errors);
assert_eq!(&value, "5");

impl<R> FluentBundle<R, IntlLangMemoizer>

pub fn new(locales: Vec<LanguageIdentifier>) -> Self

Constructs a FluentBundle. The first element in locales should be the language this bundle represents, and will be used to determine the correct plural rules for this bundle. You can optionally provide extra languages in the list; they will be used as fallback date and time formatters if a formatter for the primary language is unavailable.

Examples

use fluent_bundle::FluentBundle;
use fluent_bundle::FluentResource;
use unic_langid::langid;

let langid_en = langid!("en-US");
let mut bundle: FluentBundle<FluentResource> = FluentBundle::new(vec![langid_en]);

Errors

This will panic if no formatters can be found for the locales.

impl<R> FluentBundle<R, IntlLangMemoizer>

pub fn new_concurrent(locales: Vec<LanguageIdentifier>) -> Self

A constructor analogous to FluentBundle::new but operating on a concurrent version of IntlLangMemoizer over Mutex.

Example

use fluent_bundle::bundle::FluentBundle;
use fluent_bundle::FluentResource;
use unic_langid::langid;

let langid_en = langid!("en-US");
let mut bundle: FluentBundle<FluentResource, _> =
    FluentBundle::new_concurrent(vec![langid_en]);

Trait Implementations

impl<R> Default for FluentBundle<R, IntlLangMemoizer>

fn default() -> Self

Returns the “default value” for a type.