[
		{
			"FieldName":"IntegerField",
			"FieldValueBeg":1,
			"FieldValueEnd":2
		},
		{
			"FieldName":"StringField",
			"FieldValueBeg":"3",
			"FieldValueEnd":"4"
		}
]

  TUslovie = record
    value: string;
    value_beg: string;
    value_end: string;
  end;

Type
  TFieldType = (Stroka, Chislo);
  TFieldInfo = Record
    Type: TFieldType ;
    //
    begForChislo:integer;
    endForChislo:integer;  
    //
    begForStroka:string;
    endForStroka:string;
  End;

type
  TMyRecord = record
  strict private
    FIsNumeric: Boolean;
    FInt: Integer;
    FStr: string;
    //getters and setters
  public
    property IsNumeric: Boolean read FIsNumeric write FIsNumeric;
    property Int: Integer read GetInt write SetInt;
    property Str: string read GetString write SetString;
  end;
...
function TMyRecord.GetInt: Integer;
begin
  if IsNumeric then
    Result := FInt
  else
    raise EValueNotAvailable.Create('no no');
end;

function TMyRecord.GetString: String;
begin
  if not IsNumeric then
    Result := FString
  else
    raise EValueNotAvailable.Create('no no');
end;