lua function not returning data - mobile

Question

I am having trouble with a Lua function. I can set the return value for sendAction to a string ("test") and it will return properly. However I can't get the variable of "data" to return as it always returns nil. What am i doing wrong?
local json = require("json");
local action = {};
local action_mt = { __index = action }
---------PRIVATE FUNCTIONS------------
function action:sendAction(values, networkListener)
local data,pos,msg = "";
local params = {}; params.body = "";
for key,value in pairs(values) do
params.body = params.body .. "&" .. key .."=" .. value
end
local function networkListener( event )
if ( event.isError ) then
print( "Network error!" );
else
data,pos,msg = json.decode( event.response );
if (data.errors.count > 0) then
print("errors");
end
end
return data;
end
network.request( "http://127.0.0.1/action.php", "POST", networkListener, params )
end
------PUBLIC FUNCTIONS------
function action:new(action)
local newAction = { action = action };
return setmetatable( newAction, action_mt )
end
function action:createSession()
local data = action:sendAction( { action = "createSession" } );
print(data);
end
return action;

Answer 1

sendAction contains no return statement (in its scope). Why would you expect it to return anything?
The call to network.request is asynchronous, meaning the request actually happens in a separate thread of execution that runs parallel to your main code execution, so the request to the server and response from the server will happen after sendAction has returned.
You want to use the same model network.request does. That is, you pass a callback to sendAction which receives results when they become available. That's a very typical pattern for asynchronous code.
function action:sendAction(values, onSendActionComplete)
local params = {}; params.body = "";
for key,value in pairs(values) do
params.body = params.body .. "&" .. key .."=" .. value
end
local function networkListener( event )
if event.isError then
onSendActionComplete(false, "Network error.");
else
local data,pos,msg = json.decode( event.response );
if data.errors.count > 0 then
onSendActionComplete(false, "JSON decode error.");
else
onSendActionComplete(true, data);
end
end
end
network.request( "http://127.0.0.1/action.php", "POST", networkListener, params )
end
------PUBLIC FUNCTIONS------
function action:new(action)
local newAction = { action = action };
return setmetatable( newAction, action_mt )
end
function action:createSession()
local function onSendActionComplete(success, data)
if success then
print(data);
else
print('Error:', data)
end
end
action:sendAction( { action = "createSession" }, onSendActionComplete)
end