FirestoreBook.swift

struct FirestoreBook {
    var isbn: String
    var title: String
    var authors: [String]
    var year: Int
    var country: String
    var createdAt: Date
    var format: Format
    var award: String?
    
    enum Format: String, StringRawRepresentable {
        case paperback
        case pocket
        case ebook
    }
}

extension FirestoreBook: FirestoreModel {
    
    var documentID: String! {
        return isbn
    }
    
    var customID: String? {
        return "isbn"
    }
    
    init?(modelData: FirestoreModelData) {
        try? self.init(
            isbn: modelData.documentID,
            title: modelData.value(forKey: "title"),
            authors: modelData.value(forKey: "authors"),
            year: modelData.value(forKey: "year"),
            country: modelData.value(forKey: "country"),
            createdAt: modelData.value(forKey: "createdAt"),
            format: modelData.value(forKey: "format"),
            award: modelData.optionalValue(forKey: "award")
        )
    }
}