Build global apps: Localization by example

Translation

• Use String(localized:comment:) for localizing text

let windPerceptionLabelText = String(
  localized: "Wind is making it feel cooler", 
  comment: "Explains the wind is lowering the apparent temperature"
)

• new String(localized:defaultValue:comment) for the same English word but different translations

• Don’t assume that prepositions will be the same in other languages for interchangeable dynamic data, such as a city name & location description

• comment is really important for translators, give them the context

  • What interface element

  • What context

  • What each variable is

• When Server sends a list of supported languages, use Bundle.preferredLocalizations(from: allServerLanguages).first on phone to get the most fitting language

• for pluralized texts, use a Stringsdict file or automated grammar agreement

String(localized: "\(amountOfRain) in last ^[\(numberOfHours) hour](inflect: true).",
       comment: "Label showing how much rain has fallen in the last number of hours")

Formatters

• for unit numbers use .formatted on the number, e.g. with the .percent type

• Formatters available for almost everything (session “Formatters make data human friendly” from past years)

• Combine formatters with text

  • use UnitLength(forLocale: .current, usage: .rainfall) for the preferred unit

  • use Measurement type for unit-ful values

func expectedPrecipitationIn24Hours(for valueInMillimeters: Measurement<UnitLength>) -> String {
  // Use user's preferred measures
  let preferredUnit = UnitLength(forLocale: .current, usage: .rainfall)

  let valueInPreferredSystem = valueInMillimeters.converted(to: preferredUnit)

  // Format the amount of rainfall
  let formattedValue = valueInPreferredSystem
    .formatted(.measurement(width: .narrow, usage: .asProvided))

  let integerValue = Int(valueInPreferredSystem.value.rounded())

  // Load and use formatting string
  return String(localized: "EXPECTED_RAINFALL", 
         defaultValue: "\(integerValue) \(formattedValue) expected in next \(24)h.", 
          comment: "Label - How much precipitation (2nd formatted value, in mm or Inches) is expected in the next 24 hours (3rd, always 24).")
}

• Stringsdict entry starts with a key

  • provide for other first

  • provide any others needed per language

Swift Packages

• provide defaultLocalization in package definition

• you can now export localizations from packages, too: Go to Products > Export Localizations and choose your package

• will export as .xcloc files for translators, can be imported again

• String(localized:bundle:comment:) used in packages

  • pass .module for bundle in packages

• Localize your package, advertise supported languages

• Developers should ensure dependencies are localized & test

• Layout and SwiftUI

• don’t give UI elements a fixed height, some languages like Hindi need more line height for the same text

• Adjust a column width in a table like list to the longest label

• use Grid view in SwiftUI to implement this

• use two or more lines if needed, e.g. for German on watchOS

• Sometimes a horizontal stack can be changed to a vertical to fit

• Possible with ViewThatFits in SwiftUI now