Type Alias icu_provider_adapters::fork::ForkByKeyProvider

pub type ForkByKeyProvider<P0, P1> = ForkByErrorProvider<P0, P1, MissingDataKeyPredicate>;

Create a provider that returns data from one of two child providers based on the key.

The result of the first provider that supports a particular DataKey will be returned, even if the request failed for other reasons (such as an unsupported language). Therefore, you should add child providers that support disjoint sets of keys.

ForkByKeyProvider does not support forking between DataProviders. However, it supports forking between AnyProvider, BufferProvider, and DynamicDataProvider.

Examples

Normal usage:

use icu_locid::langid;
use icu_provider::hello_world::*;
use icu_provider::prelude::*;
use icu_provider_adapters::fork::ForkByKeyProvider;

struct DummyBufferProvider;
impl BufferProvider for DummyBufferProvider {
    fn load_buffer(
        &self,
        key: DataKey,
        req: DataRequest,
    ) -> Result<DataResponse<BufferMarker>, DataError> {
        Err(DataErrorKind::MissingDataKey.with_req(key, req))
    }
}

let forking_provider = ForkByKeyProvider::new(
    DummyBufferProvider,
    HelloWorldProvider.into_json_provider(),
);

let provider = forking_provider.as_deserializing();

let german_hello_world: DataPayload<HelloWorldV1Marker> = provider
    .load(DataRequest {
        locale: &langid!("de").into(),
        metadata: Default::default(),
    })
    .expect("Loading should succeed")
    .take_payload()
    .expect("Data should be present");

assert_eq!("Hallo Welt", german_hello_world.get().message);

Stops at the first provider supporting a key, even if the locale is not supported:

use icu_locid::{subtags::language, langid};
use icu_provider::hello_world::*;
use icu_provider::prelude::*;
use icu_provider_adapters::filter::Filterable;
use icu_provider_adapters::fork::ForkByKeyProvider;

let forking_provider = ForkByKeyProvider::new(
    HelloWorldProvider
        .into_json_provider()
        .filterable("Chinese")
        .filter_by_langid(|langid| langid.language == language!("zh")),
    HelloWorldProvider
        .into_json_provider()
        .filterable("German")
        .filter_by_langid(|langid| langid.language == language!("de")),
);

let provider: &dyn DataProvider<HelloWorldV1Marker> =
    &forking_provider.as_deserializing();

// Chinese is the first provider, so this succeeds
let chinese_hello_world = provider
    .load(DataRequest {
        locale: &langid!("zh").into(),
        metadata: Default::default(),
    })
    .expect("Loading should succeed")
    .take_payload()
    .expect("Data should be present");

assert_eq!("你好世界", chinese_hello_world.get().message);

// German is shadowed by Chinese, so this fails
provider
    .load(DataRequest {
        locale: &langid!("de").into(),
        metadata: Default::default(),
    })
    .expect_err("Should stop at the first provider, even though the second has data");

Aliased Type

struct ForkByKeyProvider<P0, P1>(/* private fields */);

Implementations

impl<P0, P1> ForkByKeyProvider<P0, P1>

pub fn new(p0: P0, p1: P1) -> Self

A provider that returns data from one of two child providers based on the key.

See ForkByKeyProvider.