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Abstract

Apple provides nice tools for internationalization and localization (See official documentation). However, we had several pains that weren't answered out of the box easily:

• Multiple .strings files to maintain: genstrings will extract NSLocalizedString strings from code, but for each IB document you internationalize - you need to have a separate .strings file, which causes painful maintenance of strings for localization. Also - this way if you already localized a common expression that appears in several files, you'll need to remember to update it for each file separately.
• Localizing a new version is very painful: When you change a view in IB, its .strings file can immediately become invalid and it is very hard to make use of the existing localizations of previous versions. This is also true for the .strings that are extracted by genstrings.
• NSLocalizedString assumes strings are in main bundle: If you want to use another localization bundle path (e.g. some path of a file you download from your server in runtime), you need to use other more complex macros.
• NSLocalizedString figures out which locale to use automatically: Which is great, but often the user wants to change this preference for your app, without changing the whole device's language.

JTLocalize was written to solve these pains:

• Unified .strings file: Collection of multiple localizable strings from multiple types of resources throughout the project. No need for separate strings file per storyboard/xib - Only one file to maintain without duplicate strings.
• Continuous translation intergration simplified: When the app changes, you don't need to localize everything again. jtlocalize command-line tools will make it easy to just send the diff for translation and merge the translated diff back.
• Configurable location of localization bundle: This allows you to easily decide to use the main bundle as default, and move to another path once you downloaded it from server. As a side effect of this, you can easily use JTLocalize to change all the English versions of your strings from server.
• Configurable preferred locale: This allows you to easily let the user choose a language without relying solely on the language taken from device's settings.

How to internationalize (Preparing your project's strings for the unified .strings file)

Internationalization is done using custom objective-c classes and simple marking mechanisms.

Adding to your project

JTLocalize can be added to an Xcode project using CocoaPods:

pod "JTLocalize"

Internationalizing UI Elements

Internationalization of UI elements works for both xibs and storyboard files.

In order to internationalize UI element (UIBotton,UILabel,UITextField, ...):

• Use the corresponding class in the JTLocalize framework (JTButton, JTLabel, JTTextField, ...) as the Custom Class of the UI element. These classes use the proper localized string when setting the text.

• In interface Builder's Document Outline, set the element's "userLabel" (Document->Label) to a string with the JTL_ prefix. This prefix is respected by our localization command-line tool for string extraction. The rest of the string in the userLabel (after the JTL_ prefix) will be used as the comment of the localization entry in the Localizable.strings files.

Internationalizing DTCoreText attributed labels

To internationalize DTCoreText elements (DTAttributedLabel) see the illustration in the example project (DTAttributedLabel+JTLocalizeExtensions, JTAttributedLabelWithLink). The reason this is only in the example project is to avoid DTCoreText dependency in the Pod.

If you want to use them (and internationalize them), add a keypath named htmlString with an html string value. In this html string value, simply put JTL("Key", "Comment") wherever you would a localized string value.

Internationalizing strings in code

To internationalize strings in the code, simply use the JTLocalizedString() macro (exactly as you would use NSLocalizedString() normally, but with a different macro):

NSString *localizedString = JTLocalizedString("Some string", "The Strings context for translation")

Swift

Swift doesn't support C-macros. We currently didn't insert any Swift functions into the Pod itself, because CocoaPods' Swift support is still in beta (as of writing these lines).

Instead, we attached a POC to our example project to show you how you can easily use JTLocalize in your Swift projects. See JTSwiftPOC.swift

How to localize

The JTLocalize framework provides the jtlocalize command line tool that integrate with the internationalization mechanisms, and simplify the localization flow.

Installation

This application requires:

• Python 2.x

Install with pip install jtlocalize, or download the latest release version:

• Release: https://pypi.python.org/pypi/jtlocalize

The standard localization flow

Usually we will use the generate, prepare_diff and merge sub-operations of the jtlocalize command-line tool, in the following manner:

• Make sure your JTLocalizable.bundle is ready with directories for all the languages you need (see appendix for more info)
• Run jtlocalize generate /path/to/project /path/to/JTLocalizable.bundle
• Run jtlocalize prepare_diff /path/to/JTLocalizable.bundle
• Translate the Localizable.strings.pending files in the different languages directories
  (convert encoding if needed, see appendix).
• Save the translated file in the proper language directory under Localizable.strings.translated
  (convert encoding if needed, see appendix).
• Run jtlocalize merge /path/to/JTLocalizable.bundle

mock_translate

Another useful sub-operation that can help you make sure you didn't forget to internationalize any strings in your app.

Example Usage:

jtlocalize mock_translate --preset chicken /path/to/Localizable.strings

Will localize the given file so that all translations are "Chicken".

word_count

Often we need to send a pending strings file to a 3rd party translation service, which charge us by a word count. To get an accurate word count of the words that actually needs to be translated, you can run: jtlocalize word_count /path/to/Localizable.strings.pending

More operations and flags

jtlocalize supports many flags and features for configuring your localization flow. You can run jtlocalize --help or jtlocalize OPERATION --help to gen information about all of them.

Updating localization bundle and preffered locale in runtime

As mentioned above, we wanted to enable easy relocation of the localization bundle out of the main app bundle, to support the use case of updating the bundle from a remote server (and as an awesome side effect - allowing us to change English strings without releasing a new version!). Also, we wanted to allow users to change preferred language.

By default, app will search for localized versions Localizable.strings in the JTLocalizable.bundle (see appendix) that is in the app bundle. Also, by default app will choose the preffered locale according to user's preferences in the iOS Settings app.

To change this behavior, you can change the path in the following manner:

[JTLocalize setLocalizationBundleToPath:NEW_PATH stringsTableName:NEW_TABLE_NAME preferredLocale:NEW_LOCALE_IDENTIFIER];

You can pass nil as NEW_PATH, NEW_TABLE_NAME or NEW_LOCALE_IDENTIFIER to use the defaults (app bundle, "Localizable", and the locale iOS decides on by default from what's available)

NEW_LOCALE_IDENTIFIER should be in the form of the ISO 639-1 code (e.g. 'en', 'fr', 'zh-Hans', 'pt-PT', etc.) and will essentially redirect the app to take the strings table from the corresponding .lproj subdir of the localization bundle. If you want to know anywhere in your app which locale is actively beeing used by JTLocalize, you can use

[JTLocalize effectiveLocale]

At JoyTunes, we use the bundle version of JTLocalizable.bundle by default. When app loads - we download an updated version from our servers to the Documents directory, and call setLocalizationBundleToPath with the path we downloaded it to. Also, by default we set prefferedLocale to nil, but once the user decides to change this from a settings screen, we call this method with the updated choice, and cache it using NSUserDefaults for next sessions.

Notice that NSBundles are automatically cached, so making this call without changing the path won't cause the bundle's content to refresh even if it was changed (but will replace the preferredLocale).

Appendices

JTLocalizable.bundle - The localization bundle

The localize bundle is the directory containing the strings files for the different languages the app is localized to.

For example:

JTLocalizable.bundle
|   +-- en.lproj
|   |   +-- Localizable.strings
|   +-- ru.lproj
|   |   +-- Localizable.strings

The jtlocalize command_line tools assume en.lproj is the default language directory (will be configurable in future). Whenever you need to add a new language, just make sure you add an empty LANGUAGE_CODE.lproj directory to the bundle before running prepare_diff.

Convert Localizable.strings from/to proper encoding

Notice: The Localizable.strings encoding is UTF16, Little Endian, with line ending set as LF.
The different scripts expect & produce the files in this encoding.

You can use:

iconv -f utf-8 -t utf-16 Localizable.strings > Localizable.new.strings

to convert utf-8 file to the format we use in the scripts.

iconv -f utf-16 -t utf-8 Localizable.strings > Localizable.new.strings

for the opposite effect.