Tim

I know Recno property has not the same funcionality used in DBISAM. But I
have a lot of code like below:

var nRec: Integer;
begin
       nRec := Table.Recno;
       // Do some record pointer changes
       Table.Recno := nRec;
end;

I think I have to change to use BookMarks (without index change) but
TBookmark is a Pointer and I have an inherited TEDBTable and I want to
create a special property RecordId or something else to act like Recno in
DBISAM. There is a manner to convert a Pointer type to an integer ? If it
could be possible I will deal internally (in the inherited component) using
Bookmarks and convert to an integer to return the result of the write method
of this property.

Regards

Eduardo

Eduardo,

<< I think I have to change to use BookMarks (without index change) but
TBookmark is a Pointer and I have an inherited TEDBTable and I want to
create a special property RecordId or something else to act like Recno in
DBISAM. There is a manner to convert a Pointer type to an integer ? >>

Just cast it, like this:

MyInteger:=Integer(MyPointer);

Under 32-bit OS's, a Pointer is an Integer, and vice-versa, so you may not
even need the cast.  However, you may want to keep it there for clarity
purposes.

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim

I am glad to receive this information.

What do you think about this approach ?

Just to remember, I am comming from DBISAM and I have many application that
uses Recno, and therefore I need to use it at least for conversion purposes.

Eduardo

Eduardo,

<< What do you think about this approach ? >>

It should work just fine.

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim

It is already working like I expect but I have to worry about FreeBookMark ?
Or it will be free after table destroy ?

THProTable = class(TEDBTable);
private
   function    GetMyRecno: Integer;
   procedure   SetMyRecno(Value: Integer);
public
  property    Recno: Integer read GetMyRecno  write SetMyRecno;
end;

function THProTable.GetMyRecno: Integer;
begin
    Result := Integer(GetBookMark);
end;

// SetMyRecno
/////////////
procedure THProTable.SetMyRecno(Value: Integer);
begin
    if BookMarkValid(Pointer(Value)) then begin
       GotoBookMark(Pointer(Value));
    end;
end;

Eduardo

Eduardo,

<< It is already working like I expect but I have to worry about
FreeBookMark ? Or it will be free after table destroy ? >>

You'll want to free the bookmarks, or else they will accumulate.  If you're
always using RecNo in a Get/Set pattern, just free the bookmark in the Set
method after the "if BookmarkValid" block like this:

procedure THProTable.SetMyRecno(Value: Integer);
begin
    if BookMarkValid(Pointer(Value)) then begin
       GotoBookMark(Pointer(Value));
    end;
    FreeBookmark(Pointer(Value));
end;

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim

I was thinking about the FreeBookMark and I tought the more elegant solution
is using a bookmark array (internal in the component) and for each
GetBookMark I hold the value in this array and don´t free it like you
describe, but when the table will be closed the component free all the array
of bookmarks. In this manner I avoid situations like below:

var nRec: Integer;
begin
       nRec := Table.Recno;
       // Do something that can produce errors
       Table.Recno := nRec;    <--- HERE ***
end;

*** Some times this code will never run and with my situation (migrating
from DBISAM) it will be painful to change to a try...except code. That is
the main reason to create this Recno property internally.

Eduardo

Eduardo,

<< I was thinking about the FreeBookMark and I tought the more elegant
solution is using a bookmark array (internal in the component) and for each
GetBookMark I hold the value in this array and don´t free it like you
describe, but when the table will be closed the component free all the array
of bookmarks. In this manner I avoid situations like  >>

Yes, I was thinking that it might be an issue.  A bookmark array will
certainly suffice in such a situation.

--
Tim Young
Elevate Software
www.elevatesoft.com