Hi.

You can override DoOnNewRecord() method.

WBR, Dmitry Beloshistov AKA [-=BDS=-]

From: IBObjects@yahoogroups.com [mailto:IBObjects@yahoogroups.com]
Sent: Tuesday, November 24, 2015 11:56 PM
To: IBObjects@yahoogroups.com
Subject: [IBO] delphi7: How to inherited and set a method in TIB_Query






I am trying to create a component descended from TIB_Query so that I can attach an OnNewRecord method handler which I almost always do manually for each TIB_Query that I drop on my project, like this one:

procedure DM1.IB_Query1OnNewRecord(Sender : TIB_Dataset);

begin

IB_Query1.FieldByName('PRODUCT_ID').asinteger := -1;

end;

And this is my attempt to subclass TIB_Query:

type

TMyIB_Query = class(TIB_Query)

private

FMyGeneratorName: string;

FMyIDField: string;

FUserOnNewRecord: TIB_DatasetEvent;

procedure MyNewRecord(Sender: TIB_Dataset);

public

constructor Create(AOwner: TComponent); override;

procedure GeneratePK;

procedure GenerateTempPK;

published

property MyGeneratorName: string read FMyGeneratorName write FMyGeneratorName;

property MyIDField: string read FMyIDField write FMyIDField;

end;



constructor TMyIB_Query.Create(AOwner: TComponent);

begin

inherited Create(AOwner);

if not (csDesigning in ComponentState) then begin

if Assigned(OnNewRecord) then // <--- OnNewRecord is always nil

FUserOnNewRecord := OnNewRecord;

OnNewRecord := MyNewRecord;

end;

end;



procedure TMyIB_Query.GeneratePK;

begin

if FieldByName(MyIDField).AsInteger < 0 then

FieldByName(MyIDField).AsInteger := Gen_ID(MyGeneratorName,1);

end;



procedure TMyIB_Query.GenerateTempPK;

begin

FieldByName(MyIDField).AsInteger := -1;

end;



procedure TMyIB_Query.MyNewRecord(Sender: TIB_Dataset);

begin

if Assigned(FUserOnNewRecord) then

FUserOnNewRecord(Sender);

end;

Usage: The inherited TMyIB_Query is supposed to assign a temporary PK of -1 for every insert.

Problem: If no OnNewRecord method is assigned to a dropped TMyIB_Query, the default method fires. However if a method is assigned to the dropped TMyIB_Query, only the assigned method fires, but not the default. Tracing in debug, it appears that OnNewRecord is always _nil_.

Please, can you tell me what did I do wrong?

(PS: This implementation works OK with TClientDataSet.)





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