Re: Lua and composition

[Petri Häkkinen <petrih3@...>]

On Mar 4, 2017, at 10:13 AM, Sean Conner <sean@conman.org> wrote:

>  I use the OOP syntactic surgar for my userdata to isolate the functions
> that work on a particular type to just that type.  For example, my socket
> class [1], I have functions that create sockets [2]:

Looks good to me! I'm not saying that OOP is always bad. The original post is about extending the existing ':' notation for a more complex case (composition), and I was trying to point out that there are probably simpler solutions to get things done. In my experience, with OOP it's very easy to over-engineer problems, or get distracted by form at the cost of functionality (been there, done that!).

> Also, I'm not polluting the
> global namespace, or the socket namespace, with functions that require a
> particular userdata to do their job.

Also an API made of free functions doesn't have to be in global namespace. The usual solution of require returning a table of public functions of a module works just fine.

>> Another advantage of the imperative style:
>> 
>> -- OOP
>> 
>> for i=1,#objs do
>>  objs[i]:do_something()
>> end
>> 
>> function myclass:do_something()
>>  -- code here
>> end
> 
>  Again, if the objs are subtly different there could be different
> implementations of do_something().  For instance, the objects could be
> sockets, where you have one socket for accepting new connections and several
> other sockets that are ongoing connections so the code for do_something()
> would be different.


In that case I would usually just make two different functions, or pass two arrays into do_something if it makes sense. Better to know the types of objects you are working with and make program flow explicit.

Petri