Re: Exposing C data via userdata and tables

[Peter Colson <pcolson@...>]

On 22/03/2005, at 6:02 PM, Wim Couwenberg wrote:

> > 1). Whether there is any problem using user data objects in a table 
> > like this (if there is then I guess I need the spooled file list user 
> > data object of option a),
>
> No problem at all.  As long as the lifetime of your userdata (i.e. its 
> __gc behaviour) is correct, go right ahead!  I'd prefer this over a 
> C/C++ implementation any day.

Good, didn't imagine there'd be a problem here.

> > 2). For option b), whether I have to instantiate and manage the Lua 
> > table internally in the package library to allow the OO-style access 
> > above (SpooledFileList:getfile, etc.) or whether I could use a basic 
> > Lua table from within Lua and tack on the SpooledFileList methods to 
> > that Lua-based table? (My feeling is I don't imagine I could do this 
> > in a clean encapsulated way using just a Lua table from within Lua 
> > really, it needs to be managed in the package...)
>
> My "style" in packaging C/C++ libs is to keep *as much* of the binding 
> in Lua itself.  It is far easier to set-up and tweak a bunch of Lua 
> scripts than their C/C++ alternatives and just as powerful.  I usually 
> put the C/C++ part as a "private" (light) userdata member in a Lua 
> object (i.e. a table).  Then you can use plain Lua tables, metatables, 
> functions etc. to decorate your Lua object system.  Moreover, the (now 
> considered private) userdata methods can be very low-level (just 
> export some existing API calls more or less 1-on-1) and make them 
> scripting friendly in the Lua object wrapper.

Yes, I get your point here. Whatever I was thinking of implementing in 
C table-wise, OO-wise, can be done just as easily in Lua. So keep as 
much as possible in the Lua scripts for ease of use. I guess coming 
from the C/C++ side I was tending to think I needed to keep some things 
on that side for overall consistency once I'd created/exposed the 
SpooledFIle userdata objects from C. As it is it's really just the 
SpooledFile userdata obects themselves that need be provided from C.


Regards,
Peter Colson.