Нужно оптимизировать код

procedure TForm1.TreeView1Change(Sender: TObject; Node: TTreeNode);
begin
    if TreeView1.Selected.Text = 'Брестская область ' then
    begin
       brest.Visible := True ;
       vitebsk.Visible := False;
       grodno.Visible := False;
       mogilev.Visible := False;
       minsk.Visible := False;
       bihov.Visible := False;
    end;

brest.Visible := True ;
       vitebsk.Visible := False;
       grodno.Visible := False;
       mogilev.Visible := False;
       minsk.Visible := False;
       bihov.Visible := False;

for i := 0 to ComponentCount - 1 do   
         if Components[i] is TButton then
           (Components[i] as TButton).visible := false;

TMyItem = class()
  text:string;
  city:string;
  button:TButton;
end;
 
TMyItems =  class(TObjectList)
...
end;
 
var 
  items:TMyItems;

uses Classes,Types,Contnrs;
TCity=class
  Name:string;
  crd:TPoint;
end;
TCities=class(TObjectList)
private
  function GetItems(index:integer):TCity;
  procedure SetItems(index:integer; value:TCity);
public
  property Items[index:integer]:TCity read GetItems write SetItems; default;
end;
 
TRegion=class
  name:string;
  Cities:TCities;
  constructor Create;
  destructor Destroy; override;
end;
TRegions=class(TObjectList)
 аналогично TCities
  property Items[index:integer]:TRegion read GetItems write SetItems; default;
end;
 
...
implementation
uses SysUtils;
 
procedure TCities.SetItems(index:integer; value:TCity);
begin
  inherited Items[index] := value;
end;
function TCities.GetItems(index:integer):TCity;
begin
  result := inherited Items[index] as TCity;
end;
 
constructor TRegion.Create;
begin
  Cities:=TCities.Create(True);
end;
destructor TRegion.Destroy;
begin
  FreeAndNil(Cities);
  inherited Destroy;
end;

procedure Tform1.FormCreate(...);
var r:TRegion;
  c:TCity;
begin
  Regions:=TRegions.Create(true);
  r:=TRegion.Create;
  r.name := 'Свердловская область';
  Regions.Add(r);
  c:=TCity.Create;
  c.Name := 'Екатеринбург';
  c.Crd:=Point(100,250);
  r.Cities.Add(c);
  c:=TCity.Create;
  c.Name:='Нижний Тагил';
  c.Crd:=Point(100,100);
 
  r:=Tregion.Create;
  r.name:='Тюменская область';
  Regions.Add(r);
  c:=TCity.Create;
  c.name:='Тюмень';
  c.Crd := Point(200,250);
  r.Cities.add(c);
  c.City := 'Талица';
  c.Crd := Point(180,220);
  r.Cities.Add(c);
  CreateTree();
end;
procedure Tform1.FromDestroy(...);
begin
   FreeAndNil(Regions);
end;