I have been following the tutorials on corona website and everything has been going well so far.
But in the tutorial "Displaying and saving score" i seem to have the following runtime error.
attempt to call field setPreferences' (a nil value)
This is the code of score.lua
local M = {}
M.score = 0
function M.init( options )
local customOptions = options or {} -- nice use of "or" operator
local opt = {}
opt.fontSize = customOptions.fontSize or 24
opt.font = customOptions.font or native.systemFont
opt.x = customOptions.x or display.contentCenterX
opt.y = customOptions.y or opt.fontSize*0.5 -- such that the score is positioned at the top, half of its font size.
opt.maxDigits = customOptions.maxDigits or 6
opt.leadingZeros = customOptions.leadingZeros or false
local prefix = ""
if ( opt.leadingZeros ) then
prefix = "0"
end
M.format = "%" .. prefix .. opt.maxDigits .. "d" -- so that its accesible in other modules.
-- Create the score display object
M.scoreText = display.newText( string.format( M.format, 0 ), opt.x, opt.y, opt.font, opt.fontSize ) -- string.format() works like printf and scanf statements
M.scoreText:setFillColor(1,0,0)
return M.scoreText
end
function M.set( value )
M.score = tonumber(value)
M.scoreText.text = string.format( M.format, M.score )
end
function M.get()
return M.score
end
function M.add( amount )
M.score = M.score + tonumber(amount)
M.scoreText.text = string.format( M.format, M.score )
end
function M.save()
print (" the score is " .. M.score)
local saved = system.setPreferences( "app", { currentScore=M.score } )
if ( saved == false) then
print ( "ERROR: could not save score" )
end
end
function M.load()
local score = system.getPreference( "app", "currentScore", "number" )
if ( score ) then
return tonumber(score)
else
print( "ERROR: could not load score (score may not exist in storage)" )
end
end
return M
This is the code of main.lua
local score = require( "score" )
local scoreText = score.init(
{
fontSize = 20,
font = "CoolCustomFont.ttf",
x = display.contentCenterX,
y = 30,
maxDigits = 7,
leadingZeros = true
})
local savedScore = score.load()
score.set( 1000 ) -- Sets the score to value
score.save()
I am aware there are other ways of keeping score, but I want to know what the problem is in my code. I googled everywhere but couldn't come up with any solution. Maybe I have made a mistake somewhere that I'm not able to identify.
Even tried a build on my smart phone, but ended up getting the same error.
From corona docs
Syntax
system.setPreferences( category, preferences )
category (required)
String. Indicates which set of preferences should be accessed on the system. Currently, only the "app" category is supported — this is the application's custom preferences defined by the Corona app developer.
preferences (required)
Table. Table of preferences to be written to storage. This table should contain key-value pairs where the key is the unique name of the preference and its value is either a boolean, number, or string.
if your M.score is nil then you might get an error
try this
local saved = system.setPreferences( "app", { currentScore=M.score or 0 } )
I am trying to convert existing python function into lua function. But my lua function is not producing same result as python function. Any help is appreciated.
Python function:
import json
test = '{"http://localhost:8080/":{"phone":{"-detail/phone detail.template.html":"5167n,a,7,2","s/motorola-xoom-with-wifi.json":"516a0,5,4,3"},"favicon.ico":"016ad,3,3,2","img/phones/motorola-xoom-with-wi-fi.":{"1.jpg":"*02s,2s,4v,h3|116da,o,l,6","2.jpg":"*02s,2s,4v,kp|116da,j,i,8","3.jpg":"*02s,2s,4v,ob|116da,o,m,8,7,,7,7,7","4.jpg":"*02s,2s,4v,rx|116da,o,m,9,8,,7,7,7","5.jpg":"*02s,2s,4v,vj|116da,p,m,a,8,,7,7,7"}}}'
def tri(param):
t = {}
for key in param:
if key not in param:
continue
if isinstance(param[key], dict) and param[key] is not None:
flat = tri(param[key])
for x in flat:
if x not in flat:
continue
t[key + x] = flat[x]
else:
t[key] = param[key]
return t
print(tri(json.loads(test)))
Lua code ( which is not producing same result as python function)
local json = require('cjson')
local test = '{"http://localhost:8080/":{"phone":{"-detail/phone-detail.template.html":"5167n,a,7,2","s/motorola-xoom-with-wi-fi.json":"516a0,5,4,3"},"favicon.ico":"016ad,3,3,2","img/phones/motorola-xoom-with-wi-fi.":{"1.jpg":"*02s,2s,4v,h3|116da,o,l,6","2.jpg":"*02s,2s,4v,kp|116da,j,i,8","3.jpg":"*02s,2s,4v,ob|116da,o,m,8,7,,7,7,7","4.jpg":"*02s,2s,4v,rx|116da,o,m,9,8,,7,7,7","5.jpg":"*02s,2s,4v,vj|116da,p,m,a,8,,7,7,7"}}}'
local function tri(param)
t = {}
for key in pairs(param) do
if param[key] == nil then end
if type(param[key]) == "table" then
flat = tri(param[key])
for k in pairs(flat) do
t[key .. k] = flat[k]
end
else
t[key] = param[key]
end
end
return t
end
print(json.encode(tri(json.decode(test))))
local function tri(param)
t = {} -- every time we call tri t will be "reset" to an empty table
for key in pairs(param) do
if param[key] == nil then end
if type(param[key]) == "table" then
flat = tri(param[key]) -- here we call tri, but we still need t!
for k in pairs(flat) do
t[key .. k] = flat[k]
end
else
t[key] = param[key]
end
end
return t
end
Making at least t global should solve that problem. But there is also no reason for flat to be global so we make it local too.
local function tri(param)
local t = {}
for key in pairs(param) do
if param[key] == nil then end
if type(param[key]) == "table" then
local flat = tri(param[key])
for k in pairs(flat) do
t[key .. k] = flat[k]
end
else
t[key] = param[key]
end
end
return t
end
Your task could be done a bit easier using json.traverse() function from this Lua JSON module.
Traversing lets you perform arbitrary operations with JSON elements on-the-fly.
This code concatenates element's path (for every JSON element except JSON containers: arrays/objects) and uses it as a key for Lua table.
local json = require'json'
local t = {}
local function callback(path, json_type, value)
if value ~= nil then -- value == nil for containers (arrays/objects)
t[table.concat(path)] = value
end
end
local test = '{"http://localhost:8080/":{"phone":{"-detail/phone detail.template.html":"5167n,a,7,2","s/motorola-xoom-with-wifi.json":"516a0,5,4,3"},"favicon.ico":"016ad,3,3,2","img/phones/motorola-xoom-with-wi-fi.":{"1.jpg":"*02s,2s,4v,h3|116da,o,l,6","2.jpg":"*02s,2s,4v,kp|116da,j,i,8","3.jpg":"*02s,2s,4v,ob|116da,o,m,8,7,,7,7,7","4.jpg":"*02s,2s,4v,rx|116da,o,m,9,8,,7,7,7","5.jpg":"*02s,2s,4v,vj|116da,p,m,a,8,,7,7,7"}}}'
json.traverse(test, callback)
-- Now t == {
-- ["http://localhost:8080/favicon.ico"] = "016ad,3,3,2",
-- ["http://localhost:8080/img/phones/motorola-xoom-with-wi-fi.1.jpg"] = "*02s,2s,4v,h3|116da,o,l,6",
-- ["http://localhost:8080/img/phones/motorola-xoom-with-wi-fi.2.jpg"] = "*02s,2s,4v,kp|116da,j,i,8",
-- ["http://localhost:8080/img/phones/motorola-xoom-with-wi-fi.3.jpg"] = "*02s,2s,4v,ob|116da,o,m,8,7,,7,7,7",
-- ["http://localhost:8080/img/phones/motorola-xoom-with-wi-fi.4.jpg"] = "*02s,2s,4v,rx|116da,o,m,9,8,,7,7,7",
-- ["http://localhost:8080/img/phones/motorola-xoom-with-wi-fi.5.jpg"] = "*02s,2s,4v,vj|116da,p,m,a,8,,7,7,7",
-- ["http://localhost:8080/phone-detail/phone detail.template.html"] = "5167n,a,7,2",
-- ["http://localhost:8080/phones/motorola-xoom-with-wifi.json"] = "516a0,5,4,3"
-- }