Overview

JSON Support

DWScript provides built-in, high-performance JSON support through the JSON object and the JSONVariant type.

Core Methods

Method Parameters Description
Parse jsonStr Parses JSON string into a JSONVariant.
Stringify value Converts a value (Record, Class, Array, etc) to a JSON string.
PrettyStringify value [, indent] Formats JSON for readability.
Serialize value Converts a native value into a JSONVariant object.
NewObject / NewArray Creates a dynamic JSON container.

Serializing vs Stringifying

While Stringify produces a JSON String, Serialize converts a native value directly into a JSONVariant object. This allows you to manipulate the structure before generating the final string.

var p := record x := 10; y := 20; end;

// Convert to JSONVariant, modify, then stringify
var j := JSON.Serialize(p);
j.x := 100;

PrintLn(j.ToString());
Result
{"x":100,"y":20}

Serialization Rules

DWScript uses a set of consistent rules for automatic serialization via JSON.Stringify:

Type Inclusion Rule
Classes Only published fields and properties are included.
Named Records Only published fields are included.
Anonymous Records All fields are automatically included.
Arrays All elements are included as a JSON array.

Example: Classes

type
  TUser = class
  published
    Name : String;
    Age : Integer;
  private
    InternalId : Integer; // Will be ignored
  end;

var u := new TUser;
u.Name := 'Alice'; u.Age := 30;
PrintLn(JSON.Stringify(u));
Result
{"Age":30,"Name":"Alice"}

Dynamic Access

Using JSONVariant, you can access keys using dot notation or array indexing.

var data := JSON.Parse('{"items": [10, 20]}');
PrintLn(data.items[0]);
Result
10

JSONVariant Helper Methods

When working with JSONVariant, several helper methods are available. Note that these must be called with parentheses () to avoid conflict with JSON field names.

Method Returns Description
Defined() Boolean Returns True if the value is not Undefined.
Length() Integer Returns the number of elements (Array) or keys (Object).
Low() Integer Returns the lowest index (usually 0).
High() Integer Returns the highest index of an array.
Add(item) Integer Appends an item to a JSON array. Returns the new index.
Push(item) Integer Alias for Add.
Delete(id) (none) Removes an item by index (Array) or key name (Object).
Swap(i, j) (none) Swaps two elements in an array.
Clone() JSONVariant Returns a deep copy of the structure.
ToString() String Returns the JSON string representation.
TypeName() String Returns 'Object', 'Array', 'String', 'Number', 'Boolean', 'Null' or 'Undefined'.
ElementName(i) String Returns the key name at the given index (for Objects).
AsInteger / AsFloat Explicit conversion helpers.
AsString / AsBoolean Explicit conversion helpers.

Specialized Parsers

For high-performance scenarios, these static methods on the JSON object parse strings directly into native Pascal arrays, bypassing JSONVariant overhead.

Method Parameters Returns
ParseIntegerArray (jsonStr) array of Integer
ParseFloatArray (jsonStr) array of Float
ParseStringArray (jsonStr) array of String

Auto-Serialization

DWScript can automatically stringify complex types like Records and Classes. Simply pass the instance to JSON.Stringify.

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