FromJSON: Difference between revisions

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(Added important note & better examples - lots of people have had headaches due to how fromJSON unpacks JSON array values into multiple values)
m (minor fixes)
 
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This function parses a [[JSON]] formatted string and unpacks the values into Lua variables. You can use [[toJSON]] to encode variables into a JSON string that can be read by this function.
This function parses a [[JSON]] formatted string and unpacks the values into Lua variables. You can use [[toJSON]] to encode variables into a JSON string that can be read by this function.


{{Important Note|1=When parsing a JSON array, [[fromJSON]] returns the elements as multiple separate values (unpacked). To mimic standard JSON decoders and store these elements together in a single Lua table, you must wrap the function call in a table constructor {}.
{{Important Note|1=When parsing a JSON array, [[fromJSON]] unpacks the elements as multiple separate values. To mimic standard JSON parsing behavior and store these elements together in a single Lua table, you must wrap the function call in a table constructor {}.
If your JSON string was generated directly by [[toJSON]], you do not need to wrap it!
If your JSON string was generated directly by [[toJSON]], you do not need to wrap it.
<syntaxhighlight lang="lua">
<syntaxhighlight lang="lua">
local jsonString = '["Apple", "Orange"]'
local jsonString = '["Apple", "Orange"]'
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===Returns===
===Returns===
Returns the parse JSON data as multiple values or a single table depending on the input JSON structure:
Returns the parsed JSON data as multiple values or a single table depending on the input JSON structure:
* Returns '''multiple separate values''' (destructured) if the root element of the JSON is an array
* Returns '''multiple separate values''' (unpacked) if the root element of the JSON is an '''array'''
* Returns a single table if the root element of the JSON is an object
* Returns a '''table''' if the root element of the JSON is an '''object'''
* Returns [[nil]] if the JSON string is invalid or malformed.
* Returns [[nil]] if the JSON string is invalid or malformed.


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This example shows how to capture all values of a JSON array in a single Lua table.
This example shows how to capture all values of a JSON array in a single Lua table.
<syntaxhighlight lang="lua">
<syntaxhighlight lang="lua">
local jsonArray = '["Apple", "Orange"]'
local jsonArray = '["Apple", "Orange", "Banana"]'


-- Put the fromJSON call inside of a table directly to capture all the values of the JSON array
-- Put the fromJSON call inside of a table directly to capture all the values of the JSON array
local fruits = {fromJSON(jsonArray)}
local fruits = {fromJSON(jsonArray)}


print(fruits[1], fruits[2]) --> Output: Apple Orange
if fruits[1] then -- Make sure the JSON was parsed correctly
    for i=1, #fruits do
        print(fruits[i])
    end
    --[[ Output:
    Apple
    Orange
    Banana
    ]]
end
 
</syntaxhighlight>
</syntaxhighlight>


Latest revision as of 15:50, 10 June 2026

This function parses a JSON formatted string and unpacks the values into Lua variables. You can use toJSON to encode variables into a JSON string that can be read by this function.


[[{{{image}}}|link=|]] Important Note: When parsing a JSON array, fromJSON unpacks the elements as multiple separate values. To mimic standard JSON parsing behavior and store these elements together in a single Lua table, you must wrap the function call in a table constructor {}.

If your JSON string was generated directly by toJSON, you do not need to wrap it. 

local jsonString = '["Apple", "Orange"]'
local fruitsTable = { fromJSON(jsonString) }

Syntax

var... fromJSON ( string json )

Required Arguments

  • json: A JSON formatted string.

Returns

Returns the parsed JSON data as multiple values or a single table depending on the input JSON structure:

  • Returns multiple separate values (unpacked) if the root element of the JSON is an array
  • Returns a table if the root element of the JSON is an object
  • Returns nil if the JSON string is invalid or malformed.

Examples

Example 1: Assigning to multiple variables

This example shows how fromJSON extracts values from a JSON array directly into separate Lua variables. 

local jsonArray = '["Desert Eagle", 24]'

local name, ammo = fromJSON(jsonArray)

print(name, ammo) --> Output: Desert Eagle  24

Example 2: Wrapping the call inside a table

This example shows how to capture all values of a JSON array in a single Lua table. 

local jsonArray = '["Apple", "Orange", "Banana"]'

-- Put the fromJSON call inside of a table directly to capture all the values of the JSON array
local fruits = {fromJSON(jsonArray)}

if fruits[1] then -- Make sure the JSON was parsed correctly
    for i=1, #fruits do
        print(fruits[i])
    end
    --[[ Output:
    Apple
    Orange
    Banana
    ]]
end

Example 3: Parsing a JSON object

local jsonObject = '{"playerName": "Alex", "score": 2500}'

local playerStats = fromJSON(jsonObject)

if playerStats then
    print(playerStats.playerName) --> Output: Alex
    print(playerStats.score)      --> Output: 2500
end

Example 4: Parsing a nested JSON object

local jsonString = '{"vehicle": "Infernus", "upgrades": {"nos": true, "paintjob": 2}}'

local vehicleInfo = fromJSON(jsonString)

if vehicleInfo then
    print(vehicleInfo.vehicle)           --> Output: Infernus
    print(vehicleInfo.upgrades.nos)      --> Output: true
    print(vehicleInfo.upgrades.paintjob) --> Output: 2
end

See Also


Retrieved from "https://wiki.multitheftauto.com/wiki/FromJSON?oldid=82829"