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TJSONString

TJSONString = class(TJSONValue)

Example​

procedure ScriptEvent(var Value: variant);
var
  Text: TJSONString;
begin
  Text := TJSONString.Create;
  try
    Text.Value := 'Ready';
    Value := Text.AsString;  // Ready, without JSON quotation marks.
  finally
    Text.Free;
  end;
end;

Usage​

TJSONString represents raw mutable Unicode text whose quoting and incomplete JSON escaping occur only in a parent container.

Additional Technical Info​

TJSONString stores one Delphi Unicode String and reports ValueType = jsString. The inherited virtual Create constructor creates a non-null node whose Value is empty. A directly created node is script-owned; a string node obtained from an object or array is borrowed and owned by its parent.

Value and inherited AsString expose raw, unquoted text. AsString = 'Ready' does not mean the complete JSON document "Ready"; quotation and escaping are applied only when an object or array serializes the child. TJSONString is also used by Velox JSON helpers for dates, times, GUIDs and enumeration names, with interpretation supplied by inherited conversion properties.

Escaping and parser behavior​

The parent encoder escapes quotation mark, reverse solidus, backspace, tab, line feed, form feed and carriage return. Escaping / is optional and deliberately omitted. However, the other control characters U+0000 through U+001F are emitted raw, contrary to RFC 8259, and UTF-16 surrogate pairing is not validated. Validate or sanitize untrusted strings before producing interoperable JSON.

The Deltics reader decodes the named escapes above, but its \uXXXX branch is unfinished: it consumes u and then appends the four hexadecimal characters literally instead of reconstructing the Unicode code point. A parsed string containing Unicode escapes therefore does not round-trip to its intended value.

Object field names are stored in each child's inherited Name, not in this Value. The object serializer writes those names without any escaping, a separate defect that applies even when the child is a TJSONString.

Empty and null strings​

An empty non-null String serializes as "". Clear or IsNull := True retains the raw payload but makes inherited AsString blank. An object checks IsNull and emits null; an array checks only ValueType and incorrectly emits "", making null indistinguishable from an empty string. Use a real TJSONNull in arrays.

The PascalScript NotNull property is incorrectly bound to IsNull and returns the same value. Inherited CopyFrom assumes another TJSONString without a runtime type check; a wrong-class call is especially unsafe because it treats unrelated field memory as a managed String. IsEqual compares type, case-sensitive name and AsString, so cleared strings compare as empty regardless of retained payload.

External references

Created 2026-07-20