How to bind a std::map to Lua with LuaBind

Question

I'm trying to expose my std::map<std::string, std::string> as a class property to Lua. I've set this method for my getter and setter:

luabind::object FakeScript::GetSetProperties()
{
    luabind::object table = luabind::newtable(L);
    luabind::object metatable = luabind::newtable(L);

    metatable["__index"] = &this->GetMeta;
    metatable["__newindex"] = &this->SetMeta;

    luabind::setmetatable<luabind::object, luabind::object>(table, metatable);

    return table;
}

This way it makes me able to do something like this in Lua:

player.scripts["movement"].properties["stat"] = "idle"
print(player.scripts["movement"].properties["stat"])

However, the code I've provided in C++ doesn't getting compiled. It tells me there is an ambiguous call to overloaded function at this line metatable["__index"] = &this->GetMeta; and the line after it. I'm not sure that I'm doing this correctly.

Error message:

error C2668: 'luabind::detail::check_const_pointer' : 
ambiguous call to overloaded function
c:\libraries\luabind-0.9.1\references\luabind\include\luabind\detail\instance_holder.hpp    75

These are SetMeta and GetMeta in FakeScript:

static void GetMeta();
static void SetMeta();

Previously I was doing this for getter method:

luabind::object FakeScript::getProp()
{
    luabind::object obj = luabind::newtable(L);

    for(auto i = this->properties.begin(); i != this->properties.end(); i++)
    {
        obj[i->first] = i->second;
    }

    return obj;
}

This works fine, but it's not letting me to use setter method. For example:

player.scripts["movement"].properties["stat"] = "idle"
print(player.scripts["movement"].properties["stat"])

In this code it just going to trigger getter method in both lines. Although if it was letting me to use setter, I wouldn't be able to get key from properties which it is ["stat"] right here.

Is there any expert on LuaBind here? I've seen most of people say they've never worked with it before.

Put the full error message as you see it, in your question please. — greatwolf
Well this is all I get. Actually I need someone to tell me how to assign functions for metatable fields in LuaBind way. See, I can change this to use a function to access my map instead of a property, but I'm concerned about user's programming style. — MahanGM
What does FakeScript::GetMeta and FakeScript::SetMeta look like? Those aren't functions you're trying to bind, they're class methods. — greatwolf

Oberon Oberon · Accepted Answer · 2013-07-18T17:02:04

You need to use the (undocumented) make_function() to make objects from functions.

metatable["__index"] = luabind::make_function(L, &this->GetMeta);
metatable["__newindex"] = luabind::make_function(L, &this->GetMeta);

Unfortunately, this (the simplest) overload of make_function is broken, but you just need to insert f as the second parameter in make_function.hpp.

How to bind a std::map to Lua with LuaBind

1 Answers