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Posted: **Fri 28 Nov 2008 08:36**

In our application we need an extension for each dataset. So we tried to extend the connection component "TMyConnection" in this way:

TMCyConnection = class(TMyConnection)
private
protected
public
User : string;
constructor Create(AOwner:TComponent); override;
destructor destroy; override;
published
end;

TMCyXQuery = class(TMyQuery)
private
FConnection : TMCyConnection;
procedure SetConnection(Connection:TMCyConnection);
protected
public
published
property Connection:TMCyConnection read FConnection write SetConnection;
end;

constructor TMCyConnection.Create(AOwner:TComponent);
begin
inherited Create(AOwner);
User := '???';
end;

procedure TMCyXQuery.SetConnection(Connection:TMCyConnection);
begin
if FConnection Connection then begin
FConnection := Connection;
end;
end;

At runtime the message "Connection is not defined." appears. At designtime setting of the connection to the above dataset type works well, setting of the property "Active" too.

We use Delphi-5 and MyDAC-5.55.0.39.

Where is the fault?

Posted: **Fri 28 Nov 2008 08:46**

What I see is logical. When you set a connection to TMCyXQuery, TMCyConnection don't have the connection params to make a connection.

Posted: **Fri 28 Nov 2008 11:02**

How can I solve my problem?

Posted: **Mon 01 Dec 2008 07:34**

You should use the following code for the TMCyXQuery class:

Code: Select all

TMCyXQuery = class(TMyQuery)
private
  function GetConnection: TMCyConnection;
  procedure SetConnection(Connection: TMCyConnection);
protected
public
published
  property Connection: TMCyConnection read GetConnection write SetConnection;
end;

procedure TMCyXQuery.SetConnection(Connection:TMCyConnection);
begin
  inherited Connection := Connection;
end;

function TMCyXQuery.GetConnection: TMCyConnection;
begin
  Result := TMCyConnection(inherited Connection);
end;

Posted: **Tue 02 Dec 2008 09:03**

Thanks for the useful help.

Devart Forums

Connection not defined by descendant of TmyConnection

Connection not defined by descendant of TmyConnection