GetChildString

function GetChildString(const aChildObjectName, aName, aDefault: String): String;

Example

procedure ScriptEvent(var Value: variant);
var
  Payload: TJSONObject;
begin
  Payload := TJSONObject.CreateFromString(
    '{"customer":{"code":"C100"}}');
  try
    Value := Payload.GetChildString('customer', 'code', 'UNKNOWN');
  finally
    Payload.Free;
  end;
end;

Usage

GetChildString returns the AsString view of a non-null nested value or the required default when either lookup path is missing or null.

Additional Technical Info

GetChildString finds a child TJSONObject, then a non-null value inside it. Both names are compared case-insensitively and the first duplicate wins. The PascalScript declaration requires aDefault, which is returned for a missing, null or wrong-type outer child and for a missing or null inner value.

The inner node is not required to be a TJSONString. The method returns its inherited AsString: String nodes yield raw unquoted text, Booleans lowercase literals, numbers their Delphi-formatted text, and arrays/objects compact serialized text. Structured results therefore inherit all array/object serializer defects.

Lookups are side-effect-free because they use FindValue; missing paths are not inserted. A non-null but empty String returns '', not the default.

External references

• RFC 8259 section 3: JSON values

Created 2026-07-20