On Tuesday 08 November 2005 21:33, L505 wrote: > >Hello, > > > >I am trying to understand what exactly generics are. I read the wiki > >page, but there are lot's of code examples and very few explanations. > >Can someone explain it to me in a (relatively) simple way? > > > >What problem is it trying to solve? > > > >And how do generics relate to interfaces? > > I had the same problem for a few years. It took me a few months/years to > first diagnose "what the fudge" templates/generics actually were, and what > problem they exactly solved. All the information about generics is pretty > non-real world and non-case study on the internet. It is also hyped by > programmers who again seem to show no real world or case studies. But I can > see how they can be useful in theory, nevertheless. > > I'm not going to give you a technical explanation on what they are, because > someone else can do that (and I don't have experience with generics, so I'm > not qualified to do so). > > Here is a vague non-technical explanation: > Basically generics helps you save some Typing and syntax in your units. You > can address several things at once with the same Type. Supposedly, this > encourages code reuse. You can address and create things via a shortcut > syntax sort of way.
The Very Big Advantage (Tm), is that you get syntax checking, while still using a type diversely. That's impossible to do (at compile-time) without generics. Probably the best example of this is something like TList: Without generics: TOrange = class ... end; TApple = class ... end; var T: TList; begin T := TList.Create(); T.Add(TApple.Create()); T.Add(TOrange.Create()); // Whoops, what was that? Now our program might crash. end; Of course, we could create a specialized TAppleList that only accepts Apples, but that's boring and hard work. A much cleaner way is generics: var T: TList<TApple>; begin T := TList<TApple>.Create(); T.Add(TApple.Create()); T.Add(TOrange.Create()); // This wont compile! The problem is prevented at compile-time! end; I hope that answers your question as to why it's a good idea :-) -- Regards, Christian Iversen _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
