Complete plurals support.

[shushper]

For now method AppLocalizations.plural supports only .zero .one and .other. It is good for the English language. But, for example, Russian needs support of .two .few and .many.

{
  "day": {
    "zero":"{} дней",
    "one": "{} день",
    "two": "{} дня",
    "few": "{} дня",
    "many": "{} дней",
    "other": "{} дней"
  }
}

It will be perfect to delegate plurals logic to a reliable library. I chose the Intl library and it works great for me. Intl package already included in dart so there is no need for external dependencies. I replaced plural method with the following code:

String plural(String key, dynamic value) {
   final res = Intl.pluralLogic(
     value,
     zero: this._resolve(key + '.zero', this._localizedStrings),
     one: this._resolve(key + '.one', this._localizedStrings),
     two: this._resolve(key + '.two', this._localizedStrings),
     few: this._resolve(key + '.few', this._localizedStrings),
     many: this._resolve(key + '.many', this._localizedStrings),
     other: this._resolve(key + '.other', this._localizedStrings),
     locale: localeName
   );

   return res.replaceFirst(RegExp(r'{}'), '$value');
}

Method _resolve should return null if it does not find a res by key. Be cause different languages may not use some plurals.