How to convert string into a table in Lua

Question

I am having a table data in string form. Sample is given below:

{"engName1":"HOLDER","validDurPeriod":3,"engName2":"INFORMATION","appStatus":2,"stayExpDate":"01/10/2012","engName3":"","appExpDate":"12/04/2010"}

How can I convert it into a proper table type variable so that I can access keys.I am new to lua and I am not aware if there is any existing method to do so.

See stackoverflow.com/questions/22632596/….

lhf
– lhf

2014-03-31 11:14:17 +00:00
Commented Mar 31, 2014 at 11:14 — lhf
– lhf, Commented Mar 31, 2014 at 11:14

pabdulin · Accepted Answer · 2014-03-31 09:35:58Z

3

There is plenty of JSON parsers available for Lua, for example dkjson:

local json = require ("dkjson")

local str = [[
{
  "numbers": [ 2, 3, -20.23e+2, -4 ],
  "currency": "\u20AC"
}
]]

local obj, pos, err = json.decode (str, 1, nil)
if err then
  print ("Error:", err)
else
  print ("currency", obj.currency)
  for i = 1,#obj.numbers do
    print (i, obj.numbers[i])
  end
end

Output:

currency    €
1   2
2   3
3   -2023
4   -4

answered Mar 31, 2014 at 9:35

pabdulin

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2 Comments

Vikram Singh Over a year ago

is this applicable on mobile platforms also. Because I am working on Kony framework for J2ME devices using lua as language..and when I tried to put this file, it is not even letting me start my app..also i tried with different json parser, then it is unable to identify keyword "require"...

pabdulin Over a year ago

@Vikram I'm not sure about that, require is a built-in function lua.org/pil/8.1.html so generally it should be there..

lhf · Accepted Answer · 2014-04-01 10:49:10Z

1

Try this code to start with

J=[[
{"engName1":"HOLDER","validDurPeriod":3,"engName2":"INFORMATION","appStatus":2,"stayExpDate":"01/10/2012","engName3":"","appExpDate":"12/04/2010"}
]]
J=J:gsub("}",",}")
L={}
for k,v in J:gmatch('"(.-)":(.-),') do
    L[k]=v   
    print(k,v)
end

You'll still need to convert some values to number and remove quotes.

Alternatively, you can let Lua do the hard work, if you trust the source string. Just replace the loop by this:

J=J:gsub('(".-"):(.-),','[%1]=%2,\n')
L=loadstring("return "..J)()

edited Apr 1, 2014 at 10:49

answered Mar 31, 2014 at 11:23

lhf

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11 Comments

Vikram Singh Over a year ago

do I have to add those square brackets into string for this operation.?? Please ask if something is not clear from my side..

hjpotter92 Over a year ago

@Vikram Yes. The square brackets will tell lua that the item inside it is a key.

lhf Over a year ago

@Vikram, for the sample data you gave, you don't need to add square brackets around keys. I just wanted to make the code a little more robust, in case keys had spaces in them.

Vikram Singh Over a year ago

@lhf: I am trying with your second approach and it is crashing at "J=J:gsub('(".-"):(.-),','[%1]=%2,\n')". I have added brackets at both ends. Is this a generic code or only given sample specific, because my actual string is having a collection as a value of one of keys.

Egor Skriptunoff Over a year ago

The last component of J is not terminated with ,, so it will not be processed in the second solution.

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