Strongly typed localization for domain grouped strings.

Localized.swift

import Foundation

protocol Domain {
    
    associatedtype Parent = Domain
    
    static var name: String { get }
    static var fullName: String { get }
}

extension Domain {
    
    static var name: String {
        return "\(self)"
    }
    
    static var fullName: String {
        return name
    }
}

extension Domain where Parent: Domain {
    
    static var fullName: String {
        return "\(Parent.fullName).\(name)"
    }
}

protocol LocalizationKey {
    
    var key: String { get }
    var keyPath: String { get }
}

extension LocalizationKey {
    
    var key: String {
        return "\(self)"
    }
    
    var keyPath: String {
        return key
    }
    
    func string(comment: String = "") -> String {
        return NSLocalizedString(self.keyPath, comment: comment)
    }
}

extension LocalizationKey where Self: Domain {
    
    var keyPath: String {
        return "\(type(of: self).fullName).\(key)"
    }
}


// MARK: Example
enum Localized {
    
    enum Friends: Domain {
        
        typealias Parent = Localized
        
        enum All: String, Domain, LocalizationKey {
            
            typealias Parent = Friends
            
            case title = "Title"
            case message = "Message"
            
            var key: String {
                return self.rawValue
            }
        }
    }
}


let title = Localized.Friends.All.title.string()