vc2.swift

extension Decoder {
    func getContext(forKey key: String) -> Any? {
        let infoKey = CodingUserInfoKey(rawValue: key)!
        return userInfo[infoKey]
    }
}
extension JSONDecoder {
    func set(context: Any?, forKey key: String) {
        let infoKey = CodingUserInfoKey(rawValue: key)!
        userInfo[infoKey] = context
    }
}