Localizing text in Swift code

In this tutorial I want to show how to translate a text string in Swift code file to a different language.

Suppose you have an English text string in your .swift code:

let text = "Flat White"

The text can be internationalized with NSLocalizedString function:

let text = NSLocalizedString("Flat White", comment: "Coffee order name")

The comment will be passed along with the text to translators. It is useful for describing the meaning of the text and/or the context it is used in.

I really like that we still have our original text “Flat White” in the code file instead of using identifiers. Thank you, Apple, I think this is more readable.

Exporting project for translation

Now let’s say we want to translate our project from English to Japanese. Choose Editor > Export for Localization... menu when project is selected in Project Navigator. The text will be exported to en.xliff file.

Translating .xliff file

  1. Copy en.xliff file to jp.xliff.
  2. Open the file and add a target-language="jp" attribute to all the <file> elements.
  1. Add <target> element with translated text under the English <source> element:
  <trans-unit id="Flat White">
      <source>Flat White</source>
      <note>Coffee order name</note>

Importing traslation back into the project

Use Editor > Import Localizations... menu and choose the jp.xliff file.

Finally, test the app with a different language

  1. Go to Product > Scheme > Edit Scheme...
  2. Choose a language form Application Language drop down.
  3. Run your app.

Replacing parts of localized text

Often we want to replace the parts of the text string with dynamic values when the app is running. It can be done with String.localizedStringWithFormat function.

  NSLocalizedString("My name is %@. I am %d years old.",
    comment: "Greeting"), name, age)

Translator can change the order in which the populated arguments are copied into the string.

I am %$2@ years old and my name is %$1@.

Localizing lower and upper case text

Here is how to change the case of a string according to local rules.

// In Turkish: "İstanbul"

// In Turkish: "istanbul"

// In Turkish: "İSTANBUL"