not able to call methods after decoding from json

I have a Lua class like below. I am using json to serialize the object and put it in a key value store. I am able to serialize the object and put it in the key value store successfully but i am not able to call any methods of the object after i retrieve the object from the key value store. I understand the json module skips the methods while encoding and my object does not have methods after decoding.

Is there a way to append methods to the class after i decode the object from json to lua ? some thing similar to function pointers in C language.

local class_name = "user_object";
user_object = {};  --user class 


function user_object.new (mobile, password, uid)

        local self = {};
        self.mobile = mobile;
        self.uid    = uid; -- generate a uid which is a running number.
        self.password = password;
        self.messages_sent = 0;
        self.put_request_count = 0;
        self.get_request_count = 0;
        self.last_time_active = "";
        self.get_tickets = {};
        self.put_tickets = {};
        self.group_message_stream = {};
        self.group_ownerships = {}; -- group names which he is owner of 
        self.group_memberships = {}; -- group names  which he is member of 
        self.sent_poke_count = 0;
   开发者_如何转开发     self.sent_poke_stream = {};
        self.recv_poke_count = 0;
        self.recv_poke_stream = {};

        function self:add_put_ticket(ticketid)
                table.insert(self.put_tickets, ticketid);
                self:incr_put_count();
                self:save();
                return;
        end 

        function self:add_get_ticket(ticketid)
                table.insert(self.get_tickets, ticketid);
                self:incr_get_count();
                self:save();
                return;
        end

---

Function in Lua are first class objects, you can store a function in any variable. The line

function self:add_put_ticket(ticketid)

is equivalent to

self.add_put_ticket = function (self, ticketid)

From there, it should be obvious what to do: define your desired methods where they are accessible and assign them to the appropriate fields after deserialization

---

You can do this with metatables.

user = { name = 'ponzao' } -- Just a table with values.
User = {}                  -- Table containing the functions.
function User:allCapsName() return self.name:upper() end -- A method.
setmetatable(user, {__index = User}) -- For unavailable keys all calls are dispatched to User.
print(user:allCapsName()) --> "PONZAO"