Paul That was just the property heirachy that popped into my mind
Neven ----- Original Message ----- From: "Paul Ritchie" <[EMAIL PROTECTED]> To: "Multiple recipients of list delphi" <[EMAIL PROTECTED]> Sent: Friday, November 02, 2001 3:36 PM Subject: RE: [DUG]: Best practice - To except or not > At the risk of not appearing to not enter into the spirit of the discussion > ;) aren't you talking about a database application? > > Therefore the number of clock cycles you can save by coding a certain way > over another is more than swamped by relatively slow database operations. > > Therefore I'd err on the side of selecting what is easiest to maintain in > the future. > > Paul. > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On > > Behalf Of Myles Penlington > > Sent: Friday, 2 November 2001 3:18 p.m. > > To: Multiple recipients of list delphi > > Subject: RE: [DUG]: Best practice - To except or not > > > > > > Take your pick. Paul is quite right in this statement. > > > > The overhead in setting up and taking down exception frames > > is reasonably > > light (something equivalent to about 4 assignments), however > > the overhead in > > raising an exception (and the OS raising an AV) is huge by comparison. > > > > Depends on the numbers of how often you expect it to fail. If > > never then I > > would tend to use the exception handler. > > > > Myles. > > > > > > Neven asked: > > > > > If you are following a trail of properties, ie > > > Datasource.DataSet.Connection > > > is it be to test for assignment/nil a each step or > > > just try except it? > > > > > > ie > > > if (Datasource <> nil) and > > > (Datasource.DataSet <> nil) and > > > (Datasource.DataSet.Connection <> nil) > > > then Result := Datasource.DataSet.Connection > > > else Result := nil; > > > or > > > > > > try > > > Result := Datasource.DataSet.Connection > > > except > > > Result := nil > > > end; > > > > From an efficiency point of view, setting up and collapsing > > exception frame > > is not free. > > > > Whether it's cheaper than the code to test all the pointers > > against nil > > would depend on how many you were testing. I haven't examined > > the generated > > code but I would not be suprised if it took quite a few > > pointer tests before > > the exception handling overhead was a net win. > > > > Now, if the exception is actually _fired_, you'd be paying > > lots of cycles so > > I wouldn't use this idiom where you expect Result to be nil > > very often. > > Exception processing itself is not cheap - it should only > > really be used for > > catching rare cases (hence the name exception I suppose :-) > > > > The efficiency concerns would put me off using this idiom, > > but from a style > > point of view, I'd say it's a matter of personal preference. > > > > TTFN, > > Paul. > > > > > > -------------------------------------------------------------- > > ------------- > > New Zealand Delphi Users group - Delphi List - > > [EMAIL PROTECTED] > > Website: http://www.delphi.org.nz > > To UnSub, send email to: [EMAIL PROTECTED] > > with body of "unsubscribe delphi" > > Web Archive at: http://www.mail-archive.com/delphi%40delphi.org.nz/ > > -------------------------------------------------------------- > > ------------- > > New Zealand Delphi Users group - Delphi List - > > [EMAIL PROTECTED] > > Website: http://www.delphi.org.nz > > To UnSub, send email to: [EMAIL PROTECTED] > > with body of "unsubscribe delphi" > > Web Archive at: http://www.mail-archive.com/delphi%40delphi.org.nz/ > > > > -------------------------------------------------------------------------- - > New Zealand Delphi Users group - Delphi List - [EMAIL PROTECTED] > Website: http://www.delphi.org.nz > To UnSub, send email to: [EMAIL PROTECTED] > with body of "unsubscribe delphi" > Web Archive at: http://www.mail-archive.com/delphi%40delphi.org.nz/ > --------------------------------------------------------------------------- New Zealand Delphi Users group - Delphi List - [EMAIL PROTECTED] Website: http://www.delphi.org.nz To UnSub, send email to: [EMAIL PROTECTED] with body of "unsubscribe delphi" Web Archive at: http://www.mail-archive.com/delphi%40delphi.org.nz/
