Localizable plist with group support from https://medium.com/@dcordero/a-different-way-to-deal-with-localized-strings-in-swift-3ea0da4cd143 based on cjlarsen Swift 4 update https://gist.github.com/cjlarsen/6961a52bd0a3b07337eab1f4322483e0

Localizer.swift

import Foundation

private class Localizer {
    
    static let sharedInstance = Localizer()
    
    lazy var localizableDictionary: NSDictionary! = {
        if let path = Bundle.main.path(forResource: "Localizable", ofType: "plist") {
            return NSDictionary(contentsOfFile: path)
        }
        
        fatalError("Localizable file NOT found")
    }()
    
    func localize(string: String) -> String {
        var localizableGroup = localizableDictionary!
        let components = string.components(separatedBy: ".")    // The char '.' separates group information. E.g. "Market.Fruit.orange"
        
        for component in components {
            guard let localizedValue = localizableGroup[component] as? NSDictionary else {
                if let localizedString = localizableGroup[component] as? String {
                    // When the localizable is a String item
                    return localizedString
                }
                assertionFailure("Missing translation for: \(string)")
                return ""
            }
            localizableGroup = localizedValue
        }
        
        // When the localizable is a Dictionary with at least a 'value' item
        guard let localizedString = localizableGroup["value"] as? String else {
            assertionFailure("Missing translation for: \(string)")
            return ""
        }
        
        return localizedString
    }
}

extension String {
    var localized: String {
        return Localizer.sharedInstance.localize(string: self)
    }
}