static func getUUIDString() ->String{
guard let uuidDefault =UserDefaults.standard.string(forKey:"yunuuid")else{
let uuidRef = CFUUIDCreate(kCFAllocatorDefault)
let strRef = CFUUIDCreateString(kCFAllocatorDefault, uuidRef)
let uuidString = (strRef!asString).replacingOccurrences(of:"-", with:"")
let uuidDefault =UserDefaults.standard
uuidDefault.set(uuidString, forKey:"yunuuid")
uuidDefault.synchronize()
returnuuidString
}
return uuidDefault
}
