To : CC : From: Dennis Chuah, [EMAIL PROTECTED] > > As an aside, I think you ought to use a strategy class to implement the > > switch between ADO and BDE. Don't conditional defines for this. > >I'm unfamiliar with the term "strategy class", care to explain? The terminology comes from Design Patterns by Gamma, et al. It is a design where you have different classes perform different actions, but share the same interface. In the above example, you would declare an abstract class (or interface) that contains all the methods and properties to persist the data to a database. You would then inherit one class that performs writing data to BDE and another that write data to ADO. These classes can be swapped in and out as required. The user of the class does not need to know whether the data is comming from BDE or ADO. The user only needs to know how to interact with the interface. This is known as the strategy pattern. The advantage is you abstract out the system dependence to a class, so if for example, you need to support another database technology, all you need to do is write another strategy class - all other code is unaffected. You can take this one step further and have different strategy classes that save data to database, out to a web server, exports to text files, etc. If you keep you strategy classes in packages, you can even load different classes during run-time! >At the moment we have a large graphing module which was written by a >contract programmer and tied very deeply to BDE specific controls. I >initially made a branch of the code in cvs and hacked the references to to >TQuery to TADOQuery, and Params to Parameters etc. etc. which I'm >currently merging with conditionals. I'm also looking through the code >and finding areas I could change to make it more DB generic, i.e. passing >TDatasets, not using Parameters but filling out the SQL fully. > >At the moment I'm mainly wanting to get back to one branch of code than >can be compiled for either ADO or BDE. No one else here has mentioned >anything about conditionals, am I the only one using/abusing them? > >Whats everyones thoughts on them? Conditionals are fine, but I think using the strategy pattern is more flexible, though a bit more work initially. I tend to use conditionals very minimally, and about the only time is when I need a piece of code to work with D1. For debugging, I tend to use asserts nowadays. Regards, Dennis. ________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com --------------------------------------------------------------------------- New Zealand Delphi Users group - Delphi List - [EMAIL PROTECTED] Website: http://www.delphi.org.nz --------------------------------------------------------------------------- New Zealand Delphi Users group - Delphi List - [EMAIL PROTECTED] Website: http://www.delphi.org.nz
