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Merge pull request #29718 from ragesoss/master

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Clarify i18n guide for how pluralization rules work by default
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Richard Schneeman 2017-07-08 12:08:18 -04:00 committed by GitHub
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guides/source/i18n.md
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@ -701,9 +701,11 @@ end
### Pluralization
In English there are only one singular and one plural form for a given string, e.g. "1 message" and "2 messages". Other languages ([Arabic](http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ar), [Japanese](http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ja), [Russian](http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ru) and many more) have different grammars that have additional or fewer [plural forms](http://cldr.unicode.org/index/cldr-spec/plural-rules). Thus, the I18n API provides a flexible pluralization feature.
In many languages — including English — there are only two forms, a singular and a plural, for
a given string, e.g. "1 message" and "2 messages". Other languages ([Arabic](http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ar), [Japanese](http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ja), [Russian](http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ru) and many more) have different grammars that have additional or fewer [plural forms](http://cldr.unicode.org/index/cldr-spec/plural-rules). Thus, the I18n API provides a flexible pluralization feature.
The `:count` interpolation variable has a special role in that it both is interpolated to the translation and used to pick a pluralization from the translations according to the pluralization rules defined by CLDR:
The `:count` interpolation variable has a special role in that it both is interpolated to the translation and used to pick a pluralization from the translations according to the pluralization rules defined in the
pluralization backend. By default, only the English pluralization rules are applied.
```ruby
I18n.backend.store_translations :en, inbox: {
@ -733,6 +735,22 @@ The translation denoted as `:one` is regarded as singular, and the `:other` is u
If the lookup for the key does not return a Hash suitable for pluralization, an `I18n::InvalidPluralizationData` exception is raised.
#### Locale-specific rules
The I18n gem provides a Pluralization backend that can be used to enable locale-specific rules. Include it
to the Simple backend, then add the localized pluralization algorithms to translation store, as `i18n.plural.rule`.
```ruby
I18n::Backend::Simple.include(I18n::Backend::Pluralization)
I18n.backend.store_translations :pt, i18n: { plural: { rule: lambda { |n| [0, 1].include?(n) ? :one : :other } } }
I18n.backend.store_translations :pt, apples: { one: 'one or none', other: 'more than one' }
I18n.t :apples, count: 0, locale: :pt
# => 'one or none'
```
Alternatively, the separate gem [rails-i18n](https://github.com/svenfuchs/rails-i18n) can be used to provide a fuller set of locale-specific pluralization rules.
### Setting and Passing a Locale
The locale can be either set pseudo-globally to `I18n.locale` (which uses `Thread.current` like, e.g., `Time.zone`) or can be passed as an option to `#translate` and `#localize`.