Jason and all,

just put this together and doing it in the AfterPrepare seems to work well.
The key concept is to use the fielddefs to instantiate TFields. This does a
kind of quasi-persistent field creation thing.

this code works against a connection to employee.gdb with qry.sql set to
select* from customer. just code AfterPrepare and the CalcFields event
handlers like this:

procedure TForm1.qryAfterPrepare(Sender: TObject);
var
i: Integer;
aField: TField;
begin
// After a prepare, the fielddefs are loaded
// qry.fieldCount=0 at this point, so the TFields haven't been created
yet.
// So we'll create the quasi-persistant fields now.

// Create fields from field defs and add to qry
for i:=0 to qry.FieldDefs.Count - 1 do begin

// instantiate a TField from the field def
aField := qry.FieldDefs[i].CreateField(qry);

// once the field is instantiated you can alter it properties
if UpperCase(aField.FieldName)='CONTACT_FIRST' then begin
aField.DisplayLabel:='First';
end;
if UpperCase(aField.FieldName)='CONTACT_LAST' then begin
aField.DisplayLabel:='Last';
end;
end;

// This is how you can add calculated fields
aField := TStringField.Create(qry);
aField.FieldName := 'Contact_Full';
aField.Calculated := True;
aField.DataSet := qry;
end;

procedure TForm1.qryCalcFields(DataSet: TDataSet);
begin
if qry.findField('Contact_Full')<>nil then begin
qry.FieldByName('Contact_Full').AsString:=
qry.FieldByName('Contact_First').AsString+' '+
qry.FieldByName('Contact_Last').AsString;
end;
end;

*************

Rob

----- Original Message -----
From: "Jason Wharton" <jwharton@...>
To: <IBObjects@yahoogroups.com>
Sent: Thursday, November 28, 2002 8:32 AM
Subject: Re: [IBO] Accessing & Adding Fields at runtime


> AfterPrepare is probably too late.
> I'm not really sure what will do it but I'm interested in what you find
out.
>
> Jason Wharton
> CPS - Mesa AZ
> http://www.ibobjects.com
>
> -- We may not have it all together --
> -- But together we have it all --
>
>
> ----- Original Message -----
> From: "Rob Schuff" <rob@...>
> To: <IBObjects@yahoogroups.com>
> Sent: Wednesday, November 27, 2002 4:32 PM
> Subject: [IBO] Accessing & Adding Fields at runtime
>
>
> > hi folks,
> >
> > I have created a component that contains a TIBOQuery. There is no
> > design-time creation of TFields. I'd don't need persistent fields but I
> do
> > need to deal with some issues and I'm asking what event to hook
> into/surface
> > to accomplish the following:
> >
> > 1. Define a calculated field and code the OnCalsFieldsEvent
> > 2. Access the fields to set some of the tfield properties such as
> > displayLabel etc.
> >
> > and lastly
> >
> > 3. I need the embedded query to not instantiate fields of type
> > TIBOFloatField but instead use the normal TFloatField.
> >
> > Seems like the afterprepare is the place to do it.
> >
> > Any suggestions greatly appreciated!
> >
> > rob
>
>
>
>
>
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