将字符串转换为lua中的映射

Question

I am quite new to lua. I trying to convert a string of the form

{"result": "success", "data":{"shouldLoad":"true"}"}

into lua map. So that I can access it like json. eg someMap[data][shouldLoad] => true

I dont have any json bindings in lua. I also tried loadstring to convert string of the form {"result" = "success", "data"={"shouldLoad"="true"}"} , which is not working.

Following, is the code snippet, where I am calling getLocation hook, which in turn returns json stringified map. Now I want to access some keys from this response body and take some decisions accordingly.

access_by_lua "
    local res = ngx.location.capture('/getLocation')

    //res.body = {"result"= "success", "data" = {"shouldLoad" = "true"}}
    local resData = loadstring('return '..res.body)()

    local shoulLoad = resData['data']['shouldLoad']
" 

When I try to load shouldLoad value, nginx error log reports error saying trying to index nil value.

How do I access key value with either of the string formats. Please help.

Answer 1

The best answer is to consider a pre-existing JSON module, as suggested by Alexey Ten. Here's the list of JSON modules from Alexey.

I also wrote a short pure-Lua json module that you are free to use however you like. It's public domain, so you can use it, modify it, sell it, and don't need to provide any credit for it. To use that module you would write code like this:

local json = require 'json'  -- At the top of your script.

local jsonStr = '{"result": "success", "data":{"shouldLoad":"true"}"}'
local myTable = json.parse(jsonStr)

-- Now you can access your table in the usual ways:
if myTable.result == 'success' then
  print('shouldLoad =', myTable.data.shouldLoad)
end