Missing Field

Use a fallback when a JSON field is missing.

missing_field.lua

local fallback = 
local text = '{"name":"Ada"}'
local name = require("cjson").decode(text).name
local city = require("cjson").decode(text).city or fallback
print("name=" .. name)
print("city=" .. city)

local fallback = 
local text = '{"name":"Ada"}'
local name = require("cjson").decode(text).name
local city = require("cjson").decode(text).city or fallback
print("name=" .. name)
print("city=" .. city)

local fallback = 
local text = '{"name":"Ada"}'
local name = require("cjson").decode(text).name
local city = require("cjson").decode(text).city or fallback
print("name=" .. name)
print("city=" .. city)

optional fields A missing JSON property becomes `nil` in Lua, so `or` can provide a default value.