JSON encode/decode out of order

andrecaribe · October 2013

When I try to read a json file and I use Json.Encode/Json.Decode (or json.encode/json.decode) my output is an valid json, with all attributes, but out of order. Example:

Code:

local f = io.open("|R|settings.json", "r")
local data = f:read("*all")
local json = Json.Decode(data)
f:close()
print(Json.Encode(json.user))

Input:
"user": {
"name": "",
"email": "",
"voucher": "",
"tickets": 1,
"facebookLike": false,
"wizardStudent": false,
"counter": {"acertadas": 0, "total": 200}
}

Output:
{"voucher":"","wizardStudent":false,"name":"","counter":{"acertadas":0,"total":200},"facebookLike":false,"tickets":1,"email":""}

Why this is important?
I need to generate an hash code (SHA1 + salt) with this data in App and server. If the order of the data is different, the SHA1 will never match. I have no idea what causes the disorder, apparently the code json.lua has nothing to do it.

@ar2rsawseen, have any idea??

Mells · October 2013

Lua tables with string keys are not ordered.

ar2rsawseen · October 2013

Unfortunately @Mells is right
you would need to create string from it yourself by combining components manually in specific order.

andrecaribe · October 2013

Thanks for quick response.

OZApps · October 2013

@andrecaribe, with a "string key" you can always get the order you want by specifying the order you want them to be in. I fail to understand your question or problem.

If you are using pairs, yes you will have an issue as the order the results are not sorted. If you have a long list that you need to use, then use a secondary table with the string keys which is indexed and iterate through this too get the values of the second. In case you are confused...

local keys = {"one", "two", "buckle", "my", "shoe"}
local data = 
  {
    one = "123456",
    shoe = "Hush Puppies",
    buckle = "Stainless Steel",
    two = "minutes to solve",
    my = "OZApps",
  }
 
for i=1, #keys do
  local res = data[keys[i]]
  print(i, res)
end

now you can change the order in keys to get what you want.

OZApps · October 2013

@andrecaribe,
if the results that are returned are not pre-determined then you need to parse the same and sort the tables yourself and use it.

keszegh · April 2017

i noticed something strange which seems to be due to the built-in native json decoder:
i have a value stored as -139.89
and the value restored is -139.88999999999999
etc with most of the values i store like this (all have 2 precision digits like this one).

is this a bug in the json decoder?

hgy29 · April 2017

It looks like a conversion issue between string (json) and float/double

keszegh · April 2017

@hgy29, can i do something with it or it has to be corrected in the gideros source code?

SinisterSoft · April 2017

I multiply the floats first then divide them when I get them back.

keszegh · April 2017

@SinisterSoft, but if after loading i process each table element one by one then what's the use of using the fast native json plugin, i could just use the lua Json implementation from before.

SinisterSoft · April 2017

It's just a quick fix.

keszegh · April 2017

@SinisterSoft, for that it's sure good enough.

keszegh · April 2017

in any case i made a ticket so that it's not forgotten:
https://github.com/gideros/gideros/issues/320

Howdy, Stranger!

Categories

In this Discussion

Top Posters

JSON encode/decode out of order

Comments

Howdy, Stranger!

Quick Links

Categories

In this Discussion

Top Posters

JSON encode/decode out of order

Comments