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LoadFromString

procedure LoadFromString(const aJSONString: string);

Example​

procedure ScriptEvent(var Value: variant);
var
  Values: TJSONArray;
begin
  Values := TJSONArray.Create;
  try
    Values.LoadFromString('1,"two",true');
    { Non-bracketed input is wrapped as [1,"two",true]. }
    Value := Values.AsString;
  finally
    Values.Free;
  end;
end;

Usage​

LoadFromString parses array text after optional first-character bracket wrapping, with empty-input retention and permissive grammar.

Additional Technical Info​

For nonempty input, LoadFromString checks the first character only. If it is not [, the method surrounds the entire string with brackets, then assigns the result through inherited AsString parsing. This permits a comma-separated sequence such as 1,"two" as shorthand for an array.

The check occurs before trimming. Input such as [1,2] is wrapped into [ [1,2]] and produces a nested array rather than the expected two items. A leading BOM character has the same wrapping effect. Normalise/validate input before calling when shape matters.

An empty string is passed to the parser unchanged; no value is read, so the existing array is retained rather than cleared. Use Erase for explicit emptying. Valid parsed content deep-replaces the old children and invalidates their borrowed references. Wrong top-level type is normally avoided by wrapping, while syntax/conversion errors raise before replacement.

The underlying parser is not strict RFC 8259 validation. It accepts missing/trailing commas and an unterminated array, ignores trailing input after the first value, does not decode \uXXXX, does not support exponent numbers correctly and parses decimal text through host locale. Parsed {} values later serialize as } because of the object serializer defect. A useful quirk is that LoadFromString('null') creates a real TJSONNull item and serializes as [null], unlike the defective AddNull.

External references

Created 2026-07-20