各位大大有個元件設計問題請教 我自行設計一個元件如下所示 TStorageMessage3 = class(TComponent) private FConnection: TADOConnection; protected public published property Connection: TADOConnection read GetConnection write setConnection; end; 在上面我設計了一個TADOConnection類型的屬性，此元件我也安裝到元件盤上 ，之後我新建一個專案，再Form上拉了一個TADOConnection的元件(名稱設為adoConn1)及上面我自行開發的元件(名稱設為AAA)，並且把AAA的Connection屬性，指定為adoConn1然後存檔，這時如果我把adoConn1刪除，則會出現錯誤訊息，感覺上是AAA元件在讀取Connection屬性時出錯，請問各位大大有沒有解決方法?

以上的問題有打錯，我重新KEY IN 如下 我自行設計一個元件如下所示 TStorageMessage3 = class(TComponent) private FConnection: TADOConnection; protected public published property Connection: TADOConnection read FConnection write FConnection; end; 在上面我設計了一個TADOConnection類型的屬性，此元件我也安裝到元件盤上 ，之後我新建一個專案，再Form上拉了一個TADOConnection的元件(名稱設為adoConn1)及上面我自行開發的元件(名稱設為AAA)，並且把AAA的Connection屬性，指定為adoConn1然後存檔，這時如果我把adoConn1刪除，則會出現錯誤訊息，感覺上是AAA元件在讀取Connection屬性時出錯，請問各位大大有沒有解決方法?

什麼地方出現 AV 的？ 您可在存取 FConnection 這個變數時加個如下的判斷:

begin
  if Assigned(FConnection) then
  begin
    // ...
  end;
end;

-- hagar.

unit Test;    interface    uses Classes, ADODB;    type
  TStorageMessage3 = class(TComponent)
  private
    FConnection: TADOConnection;
  protected
    procedure Notification(AComponent: TComponent;
      Operation: TOperation); override;
  public
  published
    property Connection: TADOConnection read FConnection write FConnection;
  end;
procedure Register;    implementation    procedure Register;
begin
  RegisterComponents('SC', [TStorageMessage3]);
end;    { TStorageMessage3 }    procedure TStorageMessage3.Notification(AComponent: TComponent;
  Operation: TOperation);
begin
  inherited Notification(AComponent, Operation);
  if (Operation = opRemove) and (FConnection <> nil) and
    (AComponent = Connection) then Connection := nil;
end;    end.

請加上Notification這個Method即可！ Ian

為何不模仿 TADODataset 。

fcfa2x您好: 提醒您PO程式碼的方式請參考版規說明 < href="http://delphi.ktop.com.tw/topic.php?TOPIC_ID=58991">http://delphi.ktop.com.tw/topic.php?TOPIC_ID=58991

直接write FConnection不好： TStorageMessage3 = class(TComponent) private FConnection: TADOConnection; procedure SetConnection(const value:TADOConnection) ; protected public published property Connection: TADOConnection read Connection write SetConnection; end; procedure SetConnection(const value:TADOConnection) ; begin FConnection := Value ; end ;

直接write FConnection不好： TStorageMessage3 = class(TComponent) private FConnection: TADOConnection; procedure SetConnection(const value:TADOConnection) ; protected public published property Connection: TADOConnection read Connection write SetConnection; end; procedure SetConnection(const value:TADOConnection) ; begin FConnection := Value ; end ;

謝謝各位大大的解答，我已經從VCL原始碼中找到答案了，但還是感謝各位大大的熱心