Is possible use a variable to parse a json's path? Like this?
json = require('json')
base={magali={pass='melancia'}}
--~ local oo = json.decode( readAll("../json/base.json") )
local oo = base
user = 'magali'
print("oo[" .. oo.magali.pass .. "]") -- work
print("oo[" .. oo.user.pass .. "]") -- does not work! How do this?
Error:
lua53: example.lua:34: attempt to index a nil value (field 'user')
stack traceback:
example.lua:34: in main chunk
[C]: in ?
Related
I'm using Latex since years but I'm new to embedded luacode (with Lualatex). Below you can see a simplified example:
\begin{filecontents*}{data.json}
[
{"firstName":"Max", "lastName":"Möller"},
{"firstName":"Anna", "lastName":"Smith"}
];
\end{filecontents*}
\documentclass[11pt]{article}
\usepackage{fontspec}
%\setmainfont{Carlito}
\usepackage{tikz}
\usepackage{luacode}
\begin{document}
\begin{luacode}
require("lualibs.lua")
local file = io.open('data.json','rb')
local jsonstring = file:read('*a')
file.close()
local jsondata = utilities.json.tolua(jsonstring)
tex.print('\\begin{tabular}{cc}')
for key, value in pairs(jsondata) do
tex.print(value["firstName"] .. ' & ' .. value["lastName"] .. '\\\\')
end
tex.print('\\hline\\end{tabular}')
\end{luacode}
\end{document}
When executing Lualatex following error occurs:
LuaTeX error [\directlua]:6: attempt to index field 'json' (a nil value) [\directlua]:6: in main chunk. \end{luacode}
When commenting the line \usepackage{fontspec} the output will be produced. Alternatively, the error can be avoided by commenting utilities.json.tolua(jsonstring) and all following lua-code lines.
So the question is: How can I use both "fontspec" package and json-data without generating an error message? Apart from this I have another question: How to enable german umlauts in output of luacode (see first "lastName" in example: Möller)?
Ah, I'm using TeX Live 2015/Debian on Ubuntu 16.04.
Thank you,
Jerome
I encountered this bug in cjson lua when I was using a script in redis 3.2 to set a particular value in a json object.
Currently, the lua in redis does not differentiate between an empty json array or an empty json object. Which causes serious problems when serialising json objects that have arrays within them.
eval "local json_str = '{\"items\":[],\"properties\":{}}' return cjson.encode(cjson.decode(json_str))" 0
Result:
"{\"items\":{},\"properties\":{}}"
I found this solution https://github.com/mpx/lua-cjson/issues/11 but I wasn't able to implement in a redis script.
This is an unsuccessful attempt :
eval
"function cjson.mark_as_array(t)
local mt = getmetatable(t) or {}
mt.__is_cjson_array = true
return setmetatable(t, mt)
end
function cjson.is_marked_as_array(t)
local mt = getmetatable(t)
return mt and mt.__is_cjson_array end
local json_str = '{\"items\":[],\"properties\":{}}'
return cjson.encode(cjson.decode(json_str))"
0
Any help or pointer appreciated.
There are two plans.
Modify the lua-cjson source code and compile redis, click here for details.
Fix by code:
local now = redis.call("time")
-- local timestamp = tonumber(now[1]) * 1000 + math.floor(now[2]/1000)
math.randomseed(now[2])
local emptyFlag = "empty_" .. now[1] .. "_" .. now[2] .. "_" .. math.random(10000)
local emptyArrays = {}
local function emptyArray()
if cjson.as_array then
-- cjson fixed: https://github.com/xiyuan-fengyu/redis-lua-cjson-empty-table-fix
local arr = {}
setmetatable(arr, cjson.as_array)
return arr
else
-- plan 2
local arr = {}
table.insert(emptyArrays, arr)
return arr
end
end
local function toJsonStr(obj)
if #emptyArrays > 0 then
-- plan 2
for i, item in ipairs(emptyArrays) do
if #item == 0 then
-- empty array, insert a special mark
table.insert(item, 1, emptyFlag)
end
end
local jsonStr = cjson.encode(obj)
-- replace empty array
jsonStr = (string.gsub(jsonStr, '%["' .. emptyFlag .. '"]', "[]"))
for i, item in ipairs(emptyArrays) do
if item[1] == emptyFlag then
table.remove(item, 1)
end
end
return jsonStr
else
return cjson.encode(obj)
end
end
-- example
local arr = emptyArray()
local str = toJsonStr(arr)
print(str) -- "[]"
I'm trying to write a function that will read sound and music states before starting my application.
The problem is: The first time it will run, there will be no data recorded.
First, I tried the suggested JSON function from here and I got this error:
Attempt to call global 'saveTable' (a nil value)
Is there a way to test if the file exists?
Then, I tried this one:
-- THIS function is just to try to find the file.
-- Load Configurations
function doesFileExist( fname, path )
local results = false
local filePath = system.pathForFile( fname, path )
--filePath will be 'nil' if file doesn,t exist and the path is "system.ResourceDirectory"
if ( filePath ) then
filePath = io.open( filePath, "r" )
end
if ( filePath ) then
print( "File found: " .. fname )
--clean up file handles
filePath:close()
results = true
else
print( "File does not exist: " .. fname )
end
return results
end
local fexist= doesFileExist("optionsTable.json","")
if (fexist == false) then
print (" optionsTable = nil")
optionsTable = {}
optionsTable.soundOn = true
optionsTable.musicOn = true
saveTable(optionsTable, "optionsTable.json") <<<--- ERROR HERE
print (" optionsTable Created")
end
The weird thing is that I'm getting an error at the saveTable(optionsTable,"optionsTable.json"). I just can't understand why.
If you have a working peace of code that handles the first time situation it will be enough to me. Thanks.
here's some code to check if the file exist you have to try and open the file first to know if it exist
function fileExists(fileName, base)
assert(fileName, "fileName is missing")
local base = base or system.ResourceDirectory
local filePath = system.pathForFile( fileName, base )
local exists = false
if (filePath) then -- file may exist wont know until you open it
local fileHandle = io.open( filePath, "r" )
if (fileHandle) then -- nil if no file found
exists = true
io.close(fileHandle)
end
end
return(exists)
end
and for usage
if fileExists("myGame.lua") then
-- do something wonderful
end
you can refer to this link for details
Here is the Pseudocode for Lempel-Ziv-Welch Compression.
pattern = get input character
while ( not end-of-file ) {
K = get input character
if ( <<pattern, K>> is NOT in
the string table ){
output the code for pattern
add <<pattern, K>> to the string table
pattern = K
}
else { pattern = <<pattern, K>> }
}
output the code for pattern
output EOF_CODE
I am trying to code this in Lua, but it is not really working. Here is the code I modeled after an LZW function in Python, but I am getting an "attempt to call a string value" error on line 8.
function compress(uncompressed)
local dict_size = 256
local dictionary = {}
w = ""
result = {}
for c in uncompressed do
-- while c is in the function compress
local wc = w + c
if dictionary[wc] == true then
w = wc
else
dictionary[w] = ""
-- Add wc to the dictionary.
dictionary[wc] = dict_size
dict_size = dict_size + 1
w = c
end
-- Output the code for w.
if w then
dictionary[w] = ""
end
end
return dictionary
end
compressed = compress('TOBEORNOTTOBEORTOBEORNOT')
print (compressed)
I would really like some help either getting my code to run, or helping me code the LZW compression in Lua. Thank you so much!
Assuming uncompressed is a string, you'll need to use something like this to iterate over it:
for i = 1, #uncompressed do
local c = string.sub(uncompressed, i, i)
-- etc
end
There's another issue on line 10; .. is used for string concatenation in Lua, so this line should be local wc = w .. c.
You may also want to read this with regard to the performance of string concatenation. Long story short, it's often more efficient to keep each element in a table and return it with table.concat().
You should also take a look here to download the source for a high-performance LZW compression algorithm in Lua...
hi i have found a tutorial on how to use post json in lua.
here is the code :
http = require("socket.http")
crypto = require("crypto")
ltn12 = require("ltn12")
url = require("socket.url")
local json = require("json")
local commands_json =
{
["message"] = "Hello",
}
print (commands_json)
local json = {}
json.api_key = "6_192116334"
json.ver = 1
json.commands_json = json.encode(commands_json)
json.commands_hash = crypto.digest(crypto.md5, json.commands_json .. 'hkjhkjhkjh')
local post = "api=" .. url.escape(Json.Encode(json))
local response = {}
local r, c, h = http.request {
url = "http://127.0.0.1/?page=api",
method = "POST",
headers = {
["content-length"] = #post,
["Content-Type"] = "application/x-www-form-urlencoded"
},
source = ltn12.source.string(post),
sink = ltn12.sink.table(response)
}
local path = system.pathForFile("r.txt", system.DocumentsDirectory)
local file = io.open (path, "w")
file:write (Json.Encode(json) .. "\n")
file:write (post .. "\n")
file:write (response[1] .. "\n")
io.close (file)
json = Json.Decode(table.concat(response,''))
native.showAlert("hey", json.commands[1].tot_nbr_rows)
now i got these error:
Windows simulator build date: Dec 9 2011 # 14:01:29
Copyright (C) 2009-2011 A n s c a , I n c .
Version: 2.0.0
Build: 2011.704
table: 0346D6D0
Runtime error
...nistrator\my documents\corona projects\json\main.lua:17: attempt to c
all field 'encode' (a nil value)
stack traceback:
[C]: in function 'encode'
...nistrator\my documents\corona projects\json\main.lua:17: in main chun
k
Runtime error: ...nistrator\my documents\corona projects\json\main.lua:17: attem
pt to call field 'encode' (a nil value)
stack traceback:
[C]: in function 'encode'
...nistrator\my documents\corona projects\json\main.lua:17: in main chun
k
i don't know why i got the error from encode.
can anyone can help me about my case?
thanks in advance ...
This includes the Json code provided externally, likely with an encode function:
local json = require("json")
This throws away your old json variable and replaces it with an empty table:
local json = {}
And this tries to call json.encode which is now undefined since you redefined json as an empty table above:
json.commands_json = json.encode(commands_json)
The solution is to pick a different variable name.