API — JSON

JSON encoding and decoding. JSON null maps to a sentinel value, not nil — a nil table value would delete the key.

picocalc.json

Functions

picocalc.json.encode(value)

Encode a Lua value as a JSON string.

• Parameters:
  • value (string | number | boolean | table): Value to encode. Use picocalc.json.null to emit JSON null.
• Returns: (string) JSON text

local text = picocalc.json.encode({ name = "pico", score = 42 })
-- '{"name":"pico","score":42}'

---

picocalc.json.decode(text)

Decode a JSON string into Lua values. JSON null decodes to the picocalc.json.null sentinel (userdata), not nil.

• Parameters:
  • text (string): JSON text
• Returns: (any) Decoded value

local data = picocalc.json.decode('{"name":"pico","score":42}')
picocalc.sys.log(data.name)  -- "pico"

---

picocalc.json.isNull(v)

Check whether a value is JSON null, without referencing the sentinel directly.

• Parameters:
  • v (any): Value to test
• Returns: (boolean) true if v is the JSON null sentinel

if picocalc.json.isNull(data.middle_name) then
    -- field is explicitly null
end

---

Constants

picocalc.json.null

Sentinel value representing JSON null. Encode it to emit null; decoded null fields compare equal to it.

local text = picocalc.json.encode({ value = picocalc.json.null })
-- '{"value":null}'

---

Example

Decoding an API response and checking for null fields.

local body = '{"name":"pico","avatar_url":null,"score":1200}'
local user = picocalc.json.decode(body)

if picocalc.json.isNull(user.avatar_url) then
    picocalc.sys.log(user.name .. " has no avatar")
else
    picocalc.sys.log("avatar: " .. user.avatar_url)
end