As of iOS 7 and Mac OS X 10.9 Mavericks, Foundation has the ability to specify localized strings according to pluralization and grammar rules. You can find more information about it in the Localized Property List File section of the Foundation release notes.

NSLocalizedString and its related macros make localizing Mac and iOS applications relatively straight-forward and simple. It falls down, however, when having to deal with strings whose conjugations change based on a dynamic count value. In such cases, you may have seen code like this:

if (count == 1) {
  return NSLocalizedString(@"1 Person", nil);
} else {
  return [NSString stringWithFormat:NSLocalizedString(@"%d People", nil), count];
}

While this works alright for English, you run into problems when targeting other locales. Consider some examples as described in the Unicode Language Plural Rules:

• Many Asian languages, like Japanese, Korean, Thai, and Simplified Chinese, do not have plural forms of nouns
• Arabic has several plural forms, including rules for zero, one, two, as well as few, many, and other, which are determined using a rather complicated base 10 divmod operation to determine the parity.

Fortunately, TTTLocalizedPluralString figures all of this out for you. You can use it just as you would NSLocalizedString, only in this case, you also have an argument for count. Here is the example from before, this time using TTTLocalizedPluralString.

return TTTLocalizedPluralString(count, @"Person", nil);

This macro points to a function that determines the plural rule for the current locale, and then does an NSBundle localized string lookup for the corresponding value. In this case, en.lproj/Localizable.strings would have two keys for this: %d Person (plural rule: one) and %d Person (plural rule: other). Other localizations would only require the keys used by that language (e.g. 1 for Japanese, and 6 for Arabic).

Here is the full list of plural rules:

• zero
• one
• two
• few
• many
• other

• Arabic (ar)
• Bulgarian (bg)
• Catalan (ca)
• Chinese (Simplified) (zh-Hans)
• Chinese (Traditional) (zh-Hant)
• Croatian (cr)
• Czech (cs)
• Danish (da)
• Dutch (nl)
• English (en)
• German (de)
• Finish (fi)
• Greek (el)
• French (fr)
• Hebrew (he)
• Hungarian (hu)
• Indonesian (id)
• Italian (it)
• Japanese (ja)
• Korean (ko)
• Latvian (lv)
• Malay (ms)
• Norwegian Bokmål (nb)
• Norwegian Nynorsk (nn)
• Polish (pl)
• Portuguese (pt)
• Romanian (ro)
• Russian (ru)
• Serbian (sr)
• Spanish (es)
• Slovak (sk)
• Slovenian (sl)
• Swedish (sv)
• Thai (th)
• Turkish (tr)
• Ukrainian (uk)
• Vietnamese (vi)

Mattt

TTTLocalizedPluralString is available under the MIT license. See the LICENSE file for more info.