Product.swift

import Firebase

class Product
{
    fileprivate static let COLLECTION_PATH = "product-feed-i18n/locales/{locale}"
    
    // ...
    
    fileprivate static var collection: CollectionReference
    {
        get
        {
            return DB.instance.collection(
                COLLECTION_PATH.replacingOccurrences(
                    of: "{locale}",
                    with: Locale.current.languageCode!
                )
            )
        }
    }
    
    // ...
}