How to parse JSON path in LUA?

[therealdb]

Hi,

I'm working on new features for my Virtual Devices Plug-in. One of the things I want to add is the ability to poll an endpoint to get power consumption.

So, I want to store the URL and the JSON path in a variable, but I'm confused on how to dynamically parse JSON paths in LUA.

I have something like this in a string variable

data.meters[1].power

and I have to extract the corresponding value from the JSON I got over HTTP.

Any suggestion is very appreciated. Thanks.

[akbooer]

Tricky.

If I understand correctly, this snippet of code may do what you need.

I have a string variable with that text in it, and a structure which includes that field (and others.) The code extracts the value of the given field...

local text = "data.meters[1].power"

local struct = {
    foo = 42,
    data = {
      meters = { {power = math.pi},  {energy = 123}, 3, 4, 5  },
      litres = 7,
    },
    bung = "qwerty"
  }

-- CODE STARTS HERE!
local x = struct
for field in text: gmatch "[^%.%[%]]+" do
  x = x[tonumber(field) or field]
end

print(x)

giving:

3.1415926535898

[therealdb]

Thanks @akbooer!

It's now implemented in v 2.1 on https://github.com/dbochicchio/Vera-VirtualDevices/