TTCP = class(TComponent) private protected FWindowsSize: Word; FPacketSize: Word; FPackets: Word; public published property WindowsSize: Word read FWindowsSize write FWindowsSize; property PacketSize: Word read FPacketSize write FPacketSize; property Packets: Word read FPackets write FPackets default 0; end; TGWNode = class(TGraphicControl) private FTCP: TTCP; published property TCP: TTCP read FTCP write SetTCP; end; 我希望 TGWNode 元件安裝完，有一個TCP的屬性可以展開，請問錯在哪？

You need to create a valid object for the property.. e.g.

unit TCP;    interface    uses
    SysUtils, Classes, Controls;    type
    TTCP = class(TComponent)
    private
    protected
        FWindowsSize: Word;
        FPacketSize: Word;
        FPackets: Word;
    public
    published
        property WindowsSize: Word read FWindowsSize write FWindowsSize;
        property PacketSize: Word read FPacketSize write FPacketSize;
        property Packets: Word read FPackets write FPackets default 0;
    end;        TGWNode = class(TGraphicControl)
    private
        FTCP: TTCP;
        procedure SetTCP(const Value: TTCP);
    public
        constructor Create(AOwner: TComponent); override;
        destructor  Destroy; override;
    published
        property TCP: TTCP read FTCP write SetTCP;
    end;    procedure Register;    implementation    procedure Register;
begin
  RegisterComponents('Samples', [TGWNode]);
end;    constructor TGWNode.Create(AOwner: TComponent);
begin
    inherited;
    FTCP := TTCP.Create(self);
end;    destructor TGWNode.DEstroy;
begin
    FTCP.Free;
    inherited;
end;    procedure TGWNode.SetTCP(const Value: TTCP);
begin
end;    end.