Manipulating JSON

type
  TCarInfo = (
    Manufacturer = 1,
    Name = 2,
    Currency = 3,
    Price = 4);

var
  Cars: array [1 .. 4] of array [Manufacturer .. Price] of string = (
    ('Ferrari','360 Modena','EUR', '250000'),
    ('Ford', 'Mustang', 'USD', '80000'),
    ('Lamborghini', 'Countach', 'EUR','300000'),
    ('Chevrolet', 'Corvette', 'USD', '100000')
  );

//…other form methods declaration 
private
  procedure SetJSON(const Value: String);
  function GetJSON: String;
public
  property JSON: String read GetJSON write SetJSON;
end;

//…then in the implementation section
function TMainForm.GetJSON: String;
begin
  Result := Memo1.Lines.Text;
end;

procedure TMainForm.SetJSON(const Value: String);
begin
  Memo1.Lines.Text := Value;
end;

procedure TMainForm.btnGenerateJSONClick(Sender: TObject);
var
  i: Integer;
  JSONCars: TJSONArray;
  Car, Price: TJSONObject;
begin
  JSONCars := TJSONArray.Create;
  try
    for i := Low(Cars) to High(Cars) do
    begin
      Car := TJSONObject.Create;
      JSONCars.AddElement(Car);
      Car.AddPair('manufacturer', Cars[i][TCarInfo.Manufacturer]);
      Car.AddPair('name', Cars[i][TCarInfo.Name]);
      Price := TJSONObject.Create;
      Car.AddPair('price', Price);
      Price.AddPair('value', TJSONNumber.Create(Cars[i][TCarInfo.Price].ToInteger));
      Price.AddPair('currency',Cars[i][TCarInfo.Currency]);
    end;
    JSON := JSONCars.ToJSON;
  finally
    JSONCars.Free;
  end;
end;

procedure TMainForm.btnModifyJSONClick(Sender: TObject);
var
  JSONCars: TJSONArray;
  Car, Price: TJSONObject;
begin
  JSONCars := TJSONObject.ParseJSONValue(JSON) 
as TJSONArray;
  try
    Car := TJSONObject.Create;
    JSONCars.AddElement(Car);
    Car.AddPair('manufacturer', 'Hennessey');
    Car.AddPair('name', 'Venom GT');
    Price := TJSONObject.Create;
    Car.AddPair('price', Price);
    Price.AddPair('value', TJSONNumber.Create(600000));
    Price.AddPair('currency', 'USD');
    JSON := JSONCars.ToJSON;
  finally
    JSONCars.Free;
  end;
end;

procedure TMainForm.btnParseJSONClick(Sender: TObject);
var
  JSONCars: TJSONArray;
  i: Integer;
  Car, JSONPrice: TJSONObject;
  CarPrice: Double;
  s, CarName, CarManufacturer, CarCurrencyType: string;
begin
  s := '';
  JSONCars := TJSONObject.ParseJSONValue(JSON) 
                                         as TJSONArray;
  if not Assigned(JSONCars) then
    raise Exception.Create('Not a valid JSON');
  try
    for i := 0 to JSONCars.Count - 1 do
    begin
      Car := JSONCars.Items[i] as TJSONObject;
      CarName := Car.GetValue('name').Value;
      CarManufacturer := Car.GetValue('manufacturer').Value;
      JSONPrice := Car.GetValue('price') as TJSONObject;
      CarPrice := (JSONPrice.GetValue('value') as TJSONNumber).AsDouble;
      CarCurrencyType := JSONPrice.GetValue('currency')
      .Value
      s := s + Format(
        'Name = %s' + sLineBreak +
        'Manufacturer = %s' + sLineBreak +
        'Price = %.0n%s' + sLineBreak +
        '-----' + sLineBreak,
        [CarName, CarManufacturer,
        CarPrice, CarCurrencyType]);
    end;
    JSON := s;
  finally
    JSONCars.Free;
  end;
end;