Scripting: JSON – Arma Reforger

JSON Format

JSON stands for JavaScript Object Notation. It is a way to present data in a simple form.

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See:

• JSON for a more informative Wikipedia article
• RFC7159 for the RFC
• ECMA-404 for the standard
• https://www.json.org/ for general details and libraries
• Mozilla's article for more information.

The parent class is always an object (the O from JSON). <syntaxhighlight lang="json"> { } </enforce>

A property is defined with its name on the left of the colon, and its value on the right. Properties and strings are defined by double-quotes ".
If another property follows, a comma is required. If no other property follows, there must be no comma.

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There can be no comments in a JSON file.

<syntaxhighlight lang="json"> { "property": 42 } </enforce> <syntaxhighlight lang="json"> { "property1": 41, "property2": "fourty-two" } </enforce>

Spacing does not matter outside of the quotes. <syntaxhighlight lang="json"> { "property1": "name", "property2": 42 } </enforce> is identical to <syntaxhighlight lang="json"> {"property1":"name","property2":42} </enforce> but for obvious readability reasons, tabs and spaces are welcome.

Boolean

A boolean can be either true or false and nothing else. <syntaxhighlight lang="json"> { "boolean1": true, "boolean2": false } </enforce>

Number

A number can be either an integer or a float. There are no quotes around it. It cannot start with a period .. Scientific notations are accepted. <syntaxhighlight lang="json"> { "number1": 42, "number2": 4.2, "number3": -33, "number4": 10e10 } </enforce>

String

Line returns cannot happen in JSON strings. The following character escape sequences are accepted:

• \b
• \f
• \r
• \n
• \t
• \"
• \\
• \/
• \u#### - see Unicode chars

<syntaxhighlight lang="json"> { "string1": "This is a string", "string2": "Is \"this\" a string?\tYes, Sir\u0021" } </enforce>

Object

<syntaxhighlight lang="json"> { "object1": { "property1": "sub-object" } } </enforce>

The null value is covered. <syntaxhighlight lang="json"> { "object1": null } </enforce>

Array

An array can contain anything: direct values, or other objects with named properties. <syntaxhighlight lang="json"> { "array1": [ 4, 5, 6 ], "array2": ["This", "is", "Sparta!"], "array3": [ { "name": "object's name", "value": 33 }, { "name": "another object, inlined", "value": 42 } ] } </enforce>

Hydration

«

« Hydration refers to the process of filling an object with data. » (source)

• Properties must be named the same in JSON and in the Enforce Script object. They are case-sensitive!
• A missing property will not fail the JSON hydration.

Example

JSON Structure

MainClass.json <syntaxhighlight lang="json"> { "m_sMessage": "Hello Message", "m_subObject": { "integerValue": 1, "booleanValue": true }; } </enforce>

Script Usage

class SecondaryJSONClass : JsonApiStruct { void SecondaryJSONClass() {} // Important, if you have a constructor it needs to take 0 parameters, as the engine will construct this class when you parse a json file. int integerValue; bool booleanValue; } class MainJSONClass : JsonApiStruct { protected string m_sMessage; // names need to match the JSON property name protected SecondaryJSONClass m_subObject; void Hydrate() { LoadFromFile("MainClass.json"); // loads JSON in the calling class Print("m_sMessage = " + m_sMessage); // Prints "Hello Message" Print("is sub-object null: " + (m_subObject == null)); if (m_subObject) { Print("sub-object/integerValue = " + m_subObject.integerValue); Print("sub-object/booleanValue = " + m_subObject.booleanValue); } } }

Serialisation

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See Serialisation - JSON.