This module writes no global values, not even the module table. Import it using
json = require ("dkjson")
Exported functions and values:
json.encode (object [, state])Create a string representing the object. Object can be a table,
a string, a number, a boolean, nil, json.null or any object with
a function __tojson in its metatable. A table can only use strings
and numbers as keys and its values have to be valid objects as
well. It raises an error for any invalid data types or reference
cycles.
state is an optional table with the following fields:
indent indent (a boolean) is set, the created string will contain
newlines and indentations. Otherwise it will be one long line.keyorder keyorder is an array to specify the ordering of keys in the
encoded output. If an object has keys which are not in this array
they are written after the sorted keys.level indent is
set. For each level two spaces are added. When absent it is set
to 0.buffer buffer is an array to store the strings for the result so they
can be concatenated at once. When it isn't given, the encode
function will create it temporary and will return the
concatenated result.bufferlen bufferlen is set, it has to be the index of the last
element of buffer.tables tables is a set to detect reference cycles. It is created
temporary when absent. Every table that is currently processed
is used as key, the value is true.When state.buffer was set, the return value will be true on
success. Without state.buffer the return value will be a string.
json.decode (string [, position [, null]])Decode string starting at position or at 1 if position was
omitted.
null is an optional value to be returned for null values. The
default is nil, but you could set it to json.null or any other
value.
The return values are the object or nil, the position of the next
character that doesn't belong to the object, and in case of errors
an error message.
Two metatables are created. Every array or object that is decoded gets
a metatable with the __jsontype field set to either array or
object. If you want to provide your own metatables use the syntax
json.decode (string, position, null, objectmeta, arraymeta)
<metatable>.__jsonorder__jsonorder can overwrite the keyorder for a specific table.
<metatable>.__jsontype__jsontype can be either "array" or "object". This is mainly useful
for tables that can be empty. (The default for empty tables is
"array").
<metatable>.__tojson (self, state)You can provide your own __tojson function in a metatable. In this
function you can either add directly to the buffer and return true,
or you can return a string. On errors nil and a message should be
returned.
json.nullYou can use this value for setting explicit null values.
json.versionSet to "dkjson 2.0".
json.quotestring (string)Quote a UTF-8 string and escape critical characters using JSON
escape sequences. This function is only necessary when you build
your own __tojson functions.
json.addnewline (state)When state.indent is set, add a newline to state.buffer and spaces
according to state.level.
When the local configuration variable
always_try_using_lpeg is set, this module tries to load LPeg to
replace the functions quotestring and decode. The speed increase
is significant. You can get the LPeg module at
http://www.inf.puc-rio.br/~roberto/lpeg/.
When LPeg couldn't be loaded, the pure Lua functions stay active.
In case you don't want this module to require LPeg on its own,
disable the option always_try_using_lpeg in the source file.
In this case you can later load LPeg support using
json.use_lpeg ()Require the LPeg module and replace the functions quotestring and
and decode with functions that use LPeg patterns.
This function returns the module table, so you can load the module
using:
json = require "dkjson".use_lpeg()
Alternatively you can use pcall so the JSON module still works when
LPeg isn't found.
json = require "dkjson"
pcall (json.use_lpeg)
json.using_lpegThis variable is set to true when LPeg was loaded successfully.
local json = require ("dkjson")
local tbl = {
animals = { "dog", "cat", "aardvark" },
instruments = { "violin", "trombone", "theremin" },
bugs = json.null,
trees = nil
}
local str = json.encode (tbl, { indent = true })
print (str)
{
"bugs":null,
"instruments":["violin","trombone","theremin"],
"animals":["dog","cat","aardvark"]
}
local json = require ("dkjson")
str = [[
{
"numbers": [ 2, 3, -20.23e+2, -4 ],
"currency": "\u20AC"
}
]]
local obj, pos, err = json.decode (str, 1, nil)
if err then
print ("Error:", err)
else
for k,v in pairs(obj) do
if type (v) == "table" then
print (k)
for k2,v2 in pairs(v) do
print ("", k2, v2)
end
else
print (k, v)
end
end
end
currency € numbers 1 2 2 3 3 -2023 4 -4