Correct software-engineering approach to make Lua bindings to my C++ classes ?

Question

I'm trying to figure out the best way to register my C++ Classes constructors with Lua (from a software design perspective, not a coding perspective)

How shall I do this ?

My Ideas:

1) Make some kind of "init Lua bindings" file which binds each of the C++ constructors that I want to have available in Lua ? (problem: this file would tend to get bigger and bigger and difficult to sync/debug)

2) Each class is responsable to register it's own constructor with my "LuaManager" Class (problem: it would be stupid to bind the same constructor to Lua over and over again for the same Class of kind A, so ideally, each kind of scriptable Class should bind it's constructor with Lua only Once when using this approach.)

Ideas, or opinions are very welcome.

Answer 1

I understand what you mean by asking

from a software design perspective, not a coding perspective

however I'm not sure there's clear distinction between the two. Or, more correctly, the coding approach you take will determine your design options. For example, if you use SWIG, the options in your question don't really make sense, since you write a separate "interface" file. If you are using luabind, the options do make sense, but I would definitely choose 1) in that case as luabind headers slow compilation dramatically and I'd like to have them included in as few compilation units as possible. If your "coding" approach doesn't have that luabind shortcoming then 2) seems like the more sensible thing to do.

Answer 2

Your second approach will work well. One way to avoid multiple registrations is to use a static initialization list approach. Each class would add a Lua registration function to a static std::set pre-main. Then you'd walk this std::set when your application starts and add each class constructor binding to your Lua runtime. This would ensure your class bindings are registered only once.