On Fri, Oct 6, 2017 at 4:49 PM, Michalis Kamburelis <michalis.ka...@gmail.com> wrote: > 2017-10-06 20:52 GMT+02:00 Marcos Douglas B. Santos <m...@delfire.net>: > [...] >>> In this case, in which you indeed want two of these features simultaneously, >>> I advise COM interfaces myself :) That's why they are documented after all. >> >> I can use it only to use reference counting. > > You can, but it's a little uncomfortable. > > If you use interfaces only for reference counting (not to share the > API between some unrelated classes), then you define a single > interface for each single class, repeating the same API -- methods, > properties. It's possible, but it's just a lot of work. I have a lot > of classes in my engine, and FPC RTL, FCL, Lazarus LCL define many > more classes --- wrapping them all in an equivalent interface, only to > get reference-counting for them, would imply a lot of work and > constant maintenance.
I use interfaces because, IMO, this is the right way to write object-oriented code. First you start with the interface that will be the contract. Then, you create one or more classes "to give life" an object which represents a real entity. Finally, every method argument or class attribute, should be an interface-type variable — most cases. The repetition here is due to the language design, but I'm OK with it. Sometimes you may have 1:1 (1 interface, 1 class) but you can have 1:N. You (or just me) don't need to create an interface with the same methods/properties to use FPC RTL, FCL, Lazarus LCL just to wrap them to use reference-counting. This might be wrong at most cases. That is code duplication. We already have this infrastructure in FPC RTL, FCL, Lazarus LCL — not perfect, but... — and we don't need to recreate them in our business, we just use them. So, for example, if I need to open a file, I will have an interface that represents a file in my business and then I will use a TFileStream class encapsulated in my own representation (class) of my interfaced. Most cases we don't need the dozens methods which many classes have — even in Java or C# do that. > In contrast, something like C++ "shared pointer" is a feature that can > be applied to any existing class, without the need to repeat it's API. > See e.g. https://en.wikipedia.org/wiki/Smart_pointer . And once we > have management operators (see Sven's pointers), we can implement > something like this in Pascal. So you could use something like > "TSharedPointer<TStringList>" and you get a reference-counted instance > of TStringList. OK, it sounds interested but would be a better design if a "modeswitch" turn on this as default for entire unit, ie, every instance will be reference-counted. Best regards, Marcos Douglas _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
