Re: Using luabind wrapped types as keys into lua tables

On Thu, Mar 04, 2010 at 02:28:41PM +1100, Greg Santucci wrote:
> Any type can be used as a key in a lua table, so I'd like to use
> references to luabind wrapped types. The problem is that different lua
> variables pointing to the same luabind C++ data are going to be seen
> as different keys from the point of view of a lua table. For example:
> 
> mypin = c.pins:at(0)
> mypin2 = c.pins:at(0)
> 
> pinmap = {}
> pinmap[mypin] = "hello"
> print(pinmap[mypin2]) -- Results in (null) printed.
> 
> -- But:
> 
> mypin = c.pins:at(0)
> mypin2 = mypin
> pinmap[mypin] = "hello"
> pinr(pinmap[mypin2]) -- Results in "hello" printed, no problem
> 
> mypin and mypin2 can't be used as the same key from the point of view
> of a lua table.
> 
> Is there a way to get to the raw data pointer, so that can be used as a key
> instead?

You could write a small function that returns it:

  void get_raw_key(lua_State* L, pin const& p)
  {
      lua_pushlightuserdata(L, &p);
  }

  ...

  module(L) [
      class_<pin>("pin")
        .def("raw_key", &get_raw_key)
  ];

-- 
Daniel Wallin
BoostPro Computing
http://www.boostpro.com

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