How to make a TCollectionItem contain a TCollection #109

{ ... }
type
  TYourCollectionItem = class;
  TYourCollection = class;
  TColControl = class;

  TYourCollectionItem = class(TCollectionItem)
  protected
    FFirstString: string;
    FChildCollection: TYourCollection;
    procedure SetIndex(Value: Integer); override;
    function GetDisplayName: string; override;
  public
    constructor Create(Collection: TCollection); override;
    destructor Destroy; override;
    procedure Assign(Source: TPersistent); override;
  published
    property FirstString: string read FFirstString write FFirstString;
    property ChildCollection: TYourCollection
      read FChildCollection write FChildCollection;
  end;

  TYourCollection = class(TOwnedCollection)
  protected
    function GetItem(Index: Integer): TYourCollectionItem;
    procedure SetItem(Index: Integer; Value: TYourCollectionItem);
  public
    constructor Create(AOwner: TPersistent);
    property Items[Index: Integer]: TYourCollectionItem
      read GetItem write SetItem;
  end;

  TColControl = class(TComponent)
  protected
    FCollection: TYourCollection;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
  published
    property Collection: TYourCollection
      read FCollection write FCollection;
  end;

{ ... }

constructor TYourCollectionItem.Create(Collection: TCollection);
begin
  inherited Create(Collection);
  FChildCollection := TYourCollection.Create(Collection.Owner);
end;

destructor TYourCollectionItem.Destroy;
begin
  FChildCollection.Free;
  inherited Destroy;
end;

procedure TYourCollectionItem.SetIndex(Value: Integer);
begin
  inherited SetIndex(Value);
  ShowMessage(IntToStr(Value));
end;

function TYourCollectionItem.GetDisplayName: string;
begin
  Result := FFirstString;
end;

procedure TYourCollectionItem.Assign(Source: TPersistent);
begin
  FFirstString := TYourCollectionItem(Source).FFirstString;
  FChildCollection.Assign(TYourCollectionItem(Source).ChildCollection);
end;

constructor TYourCollection.Create(AOwner: TPersistent);
begin
  inherited Create(AOwner, TYourCollectionItem);
end;

function TYourCollection.GetItem(Index: Integer): TYourCollectionItem;
begin
  Result := TYourCollectionItem(inherited GetItem(Index));
end;

procedure TYourCollection.SetItem(Index: Integer;
  Value: TYourCollectionItem);
begin
  inherited SetItem(Index, Value);
end;

constructor TColControl.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FCollection := TYourCollection.Create(Self);
end;

destructor TColControl.Destroy;
begin
  FCollection.Free;
  FCollection := nil;
  inherited Destroy;
end;