AutoLocalize for stroryboards and xibs.

AutoLocalize.swift

import UIKit

private func AutoLocalize(_ string: String?) -> String? {
    guard let string = string else {
        return nil
    }
    if string.hasPrefix("%") {
        return NSLocalizedString(string, comment: "")
    }
    return string
}

extension UIViewController {
    @objc func autoLocalize() {
        if let tabBarController = self.tabBarController {
            for viewController in tabBarController.viewControllers ?? [] {
                if let tabBarItem = viewController.tabBarItem {
                    tabBarItem.title = AutoLocalize(tabBarItem.title)
                }
            }
        }

        let item = navigationItem
        item.title = AutoLocalize(item.title)
        item.prompt = AutoLocalize(item.prompt)
        item.leftBarButtonItem?.title = AutoLocalize(item.leftBarButtonItem?.title)
        item.rightBarButtonItem?.title = AutoLocalize(item.rightBarButtonItem?.title)
        item.backBarButtonItem?.title = AutoLocalize(item.backBarButtonItem?.title)

        view.autoLocalize()
    }
}

extension UIView {
    @objc func autoLocalize() {
        for view in subviews {
            view.autoLocalize()
        }
    }
}

extension UILabel {
    override func autoLocalize() {
        super.autoLocalize()

        let localizedText = AutoLocalize(text)
        if localizedText == text {
            return
        }
        text = localizedText
    }
}

extension UIButton {
    override func autoLocalize() {
        super.autoLocalize()
        setTitle(AutoLocalize(title(for: .normal)), for: .normal)
        setTitle(AutoLocalize(title(for: .highlighted)), for: .highlighted)
        setTitle(AutoLocalize(title(for: .selected)), for: .selected)
        setTitle(AutoLocalize(title(for: .disabled)), for: .disabled)
    }
}

extension UISegmentedControl {
    override func autoLocalize() {
        super.autoLocalize()
        for index in (0..<numberOfSegments) {
            setTitle(AutoLocalize(titleForSegment(at: index)), forSegmentAt: index)
        }
    }
}

extension UITextField {
    override func autoLocalize() {
        super.autoLocalize()
        text = AutoLocalize(text)
        placeholder = AutoLocalize(placeholder)
    }
}

extension UITextView {
    override func autoLocalize() {
        super.autoLocalize()
        text = AutoLocalize(text)
    }
}

extension UISearchBar {
    override func autoLocalize() {
        super.autoLocalize()
        text = AutoLocalize(text)
        placeholder = AutoLocalize(placeholder)
        prompt = AutoLocalize(prompt)
        if let scopeButtonTitles = self.scopeButtonTitles {
            var translatedTitles = [String]()
            for title in scopeButtonTitles {
                translatedTitles.append(AutoLocalize(title) ?? "")
            }
            self.scopeButtonTitles = translatedTitles
        }
    }
}

extension UIToolbar {
    override func autoLocalize() {
        for item in items ?? [] {
            item.title = AutoLocalize(item.title)
        }
    }
}