Solved

DataSet Before Post event

Posted on 2000-02-28
7
410 Views
Last Modified: 2010-04-04
Is it possible to access the existing value of a field(ie the value before this pending post)within this event handler WITHOUT enabling cached updates?

If so, how?

Many thanks
0
Comment
Question by:dasmi
7 Comments
 
LVL 8

Expert Comment

by:ZifNab
ID: 2564753
what about the BeforePost event?

Zif.
0
 
LVL 9

Expert Comment

by:ITugay
ID: 2564991
If you directly modifying field, for example by TDBEdit, last field value became unavalable. You cannot access last field value by simply way. You can try extract it from database by another Query only :(
0
 
LVL 9

Expert Comment

by:ITugay
ID: 2565004
Hmmm... I forget about.....
.... if you use IBX components, it possible.
0
Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
LVL 27

Expert Comment

by:kretzschmar
ID: 2565011
listening . . .
0
 
LVL 2

Accepted Solution

by:
kubeerja earned 50 total points
ID: 2566330
a simple way is to save it in a variable before Edit and check that value before post.

other wise you need to extract the value from the Active buffer of the DataSet then you can try this function

function TForm1.fDbiGetField(hTmpCur: hDBICur; FieldNo: Word): Variant;

var
  Props: CURProps;
  pFlds, pOldFlds: pFLDDesc;
  pRecBuf: pBYTE;
  FieldString: string;
  FieldINT16: Smallint;
  FieldINT32: Longint;
  FieldUINT16: Word;
  FieldFLOAT: Double;
  Blank: LongBool;
begin
  if (FieldNo < 1) then
    raise EDatabaseError.Create('Field number index is 1 based');

  Check(DbiGetCursorProps(hTmpCur, Props));
  pFlds := AllocMem(Props.iFields * sizeof(FLDDesc));
  pOldFlds := pFlds;

  pRecBuf := AllocMem(Props.iRecBufSize * sizeof(BYTE));
  try
    Check(DbiGetFieldDescs(hTmpCur, pFlds));
    Inc(pFlds, FieldNo - 1);
    Check(DbiGetRecord(hTmpCur, dbiNOLOCK, pRecBuf, nil));
    case pFlds.iFldType of
      fldDATE, fldTIME, fldTIMESTAMP, fldUNKNOWN, fldBLOB, fldBOOL, fldBCD:
        raise EDBEngineError.Create(DBIERR_NOTSUPPORTED);
      fldZSTRING:
      begin
        SetLength(FieldString, pFlds.iUnits1 + 1);

        Check(DbiGetField(hTmpCur, FieldNo, pRecBuf,
          pBYTE(PChar(FieldString)), Blank));
        SetLength(FieldString, StrLen(PChar(FieldString)));
        Result := FieldString;
      end;
      fldINT16:
      begin
        Check(DbiGetField(hTmpCur, FieldNo, pRecBuf, pBYTE(@FieldINT16),
          Blank));
        Result := FieldINT16;
      end;
      fldUINT16:
      begin
        Check(DbiGetField(hTmpCur, FieldNo, pRecBuf, pBYTE(@FieldUINT16),

          Blank));
        Result := FieldUINT16;
      end;
      fldFLOAT:
      begin
        Check(DbiGetField(hTmpCur, FieldNo, pRecBuf, pBYTE(@FieldFLOAT),
          Blank));
        Result := FieldFLOAT;
      end;
      fldINT32, fldUINT32:
      begin
        Check(DbiGetField(hTmpCur, FieldNo, pRecBuf, pBYTE(@FieldINT32),
          Blank));
        Result := FieldINT32;
      end;
    end;
  finally
    FreeMem(pOldFlds, Props.iFields * sizeof(FLDDesc));
    FreeMem(pRecBuf, Props.iRecBufSize * sizeof(BYTE));
  end;
end;

you can call it like this

Label4.Caption:=VarToStr(fDbiGetField(Table1.Handle,Table1.FieldByName('tname').Index + 1)) ;
0
 

Author Comment

by:dasmi
ID: 2566674
It works.

It is a solution which demonstrates a good knowledge of the underlying DB engine. What a great pity it is necessary to go to these lengths to simply get the existing field value(s).

Thank you very much for your prompt response with a fully working solution. I am impressed with the experts exchange service in general, and with kubeerja in particular.

0
 
LVL 2

Expert Comment

by:kubeerja
ID: 2566892
Thank you, :-)
0

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Objective: - This article will help user in how to convert their numeric value become words. How to use 1. You can copy this code in your Unit as function 2. than you can perform your function by type this code The Code   (CODE) The Im…
Creating an auto free TStringList The TStringList is a basic and frequently used object in Delphi. On many occasions, you may want to create a temporary list, process some items in the list and be done with the list. In such cases, you have to…
This video shows how to use Hyena, from SystemTools Software, to bulk import 100 user accounts from an external text file. View in 1080p for best video quality.

856 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question