Have you ever wondered how to convert and/or use alpha 2 and alpha 3 country codes seamlessly with native Swift Locale? Here is the answer: There is a tricky, very cost-efficient that can guarantee to find valid ISO Alpha-2 and Alpha-3 country codes (ISO 3166 international standard). NO EXTERNAL FILE IS NEEDED!

LocaleAlphaCode.swift

public extension Locale {
	
	private static var availableRegions: [Locale] = { Locale.availableIdentifiers.map { Locale(identifier: $0) } }()
	
	init?(isoCode: String, from: Locale = .autoupdatingCurrent) {
		guard let locale = from.locale(isoCode: isoCode) else { return nil }
		self = locale
	}
	
	func alpha2Code(from isoCode: String) -> String? {
		let regionName = localizedString(forRegionCode: isoCode) ?? ""
		return Self.availableRegions.first(where: { localizedString(forRegionCode: $0.regionCode ?? "") == regionName })?.regionCode
	}
	
	func locale(isoCode: String) -> Locale? {
		let alpha2Code = alpha2Code(from: isoCode)
		var matchingLocale: Locale?
		
		for region in Self.availableRegions {
			if region.regionCode == alpha2Code {
				if region.languageCode == languageCode {
					return region
				} else if matchingLocale == nil {
					matchingLocale = region
				}
			}
		}
		
		return matchingLocale
	}
}

// Usage in playground

Locale(isoCode: "ARE") // United Arab Emirates
Locale(isoCode: "are") // United Arab Emirates
Locale(isoCode: "ar") // Argentina
Locale(isoCode: "br") // Brazil
Locale(isoCode: "bra") // Brazil
Locale(isoCode: "BRA") // Brazil
Locale(isoCode: "US") // United States of America
Locale(isoCode: "USA") // United States of America
Locale(isoCode: "ARE", from: Locale(identifier: "en")) // English - United Arab Emirates
Locale(isoCode: "ARE", from: Locale(identifier: "ar")) // Arabic - United Arab Emirates
Locale(identifier: "en").locale(isoCode: "br") // English - Brazil
Locale(identifier: "es").locale(isoCode: "mx") // Spanish - Mexico

Locale.autoupdatingCurrent.alpha2Code(from: "ARE") // AE
Locale.autoupdatingCurrent.alpha2Code(from: "are") // AE
Locale.autoupdatingCurrent.alpha2Code(from: "aRe") // AE
Locale.autoupdatingCurrent.alpha2Code(from: "ae") // AE
Locale.autoupdatingCurrent.alpha2Code(from: "Ae") // AE