Type Definition fluent_bundle::FluentBundle

type FluentBundle<R> = FluentBundleBase<R, IntlLangMemoizer>;

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;

let ftl_string = String::from("intro = Welcome, { $name }.");
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.");

let mut args = FluentArgs::new();
args.add("name", FluentValue::from("Rustacean"));

let msg = bundle.get_message("intro").expect("Message doesn't exist.");
let mut errors = vec![];
let pattern = msg.value.expect("Message has no value.");
let value = bundle.format_pattern(&pattern, Some(&args), &mut errors);
assert_eq!(&value, "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, FluentBundle is a specialization of [FluentBundleBase] which works with an IntlMemoizer over RefCell. In scenarios where the memoizer must work concurrently, there's an implementation of IntlMemoizer that uses Mutex and there's concurrent::FluentBundle which works with that.