Photo.swift's dictionary convenience initializer

Photo.swift's convenience init(dictionary).swift

convenience init(dictionary: [String: Any]) {
    let description = dictionary["description"] as! String? ?? ""
    let postedBy = dictionary["postedBy"] as! String? ?? ""
    let date = dictionary["date"] as! Date? ?? Date()
    self.init(image: UIImage(), description: description, postedBy: postedBy, date: date, documentUUID: "")
}