CountryCode

enum CountryCode: String {

    case us = "USA"
    case zh = "China"
    case fr = "France"
    case ru = "Russia"

    var locale: Locale {
        let identifier: String

        switch self {
        case .us: identifier = "en_US"
        case .zh: identifier = "zh_CN"
        case .fr: identifier = "fr"
        case .ru: identifier = "ru_RU"
        }

        return Locale(identifier: identifier)
    }

}

 func changeLocation() {
    guard let title = countries.titleForSegment(at: countries.selectedSegmentIndex),
        let country = CountryCode(rawValue: title) else {
            return
    }

    convert(country.locale)
}