CODEWITHSUNDEEP
c++lualuajit
JerzySBG
JerzySBG

Reputation: 109

LuaJIT and C++ - call to Table.Method() does not work in loadstring/pcall

I got 2 functions that register Lua table and method in C++:

void LuaScriptInterface::registerTable(const std::string& tableName)
{
    // _G[tableName] = {}
    lua_newtable(luaState);
    lua_setglobal(luaState, tableName.c_str());
}

void LuaScriptInterface::registerMethod(const std::string& globalName, const std::string& methodName, lua_CFunction func)
{
    // globalName.methodName = func
    lua_getglobal(luaState, globalName.c_str());
    lua_pushcfunction(luaState, func);
    lua_setfield(luaState, -2, methodName.c_str());

    // pop globalName
    lua_pop(luaState, 1);
}

It registers some methods:

registerTable("Game");
// Game.getHouses()
registerMethod("Game", "getHouses", LuaScriptInterface::luaGameGetHouses);

Then I call in Lua:

local param = "print( Game.getHouses() )"
pcall(loadstring(param))

I got problem with param. Calls and results:

1. print(Game.getHouses())
2. print(Game['getHouses']())
3. print( Game.getHouses() ) -- added spaces
4. print( Game['getHouses']() ) -- added spaces
5. local var = Game.getHouses() print(#var)
6. local var = Game['getHouses']() print(#var)
7. local var = #Game.getHouses() print(var)
8. local var = #Game['getHouses']() print(var)
9. local var = # Game.getHouses() print(var) -- added space

Results:

1. attempt to call a nil value
2. table: 0x4351fdd0
3. table: 0x42ce6b88
4. table: 0x426513c0
5. 1010
6. 1010 
7. attempt to call a nil value
8. 1010
9. 1010

Can anyone tell me a reason, why it does not work in loadstring/pcall?

Can I make it work in loadstring/pcall somehow?

EDIT:

After 2 hours of debugging. I found out, that client that I use to communicate with server - that executes LUA - does some regex on string that I send (I still don't know why, but it's not LUA related) :)

Upvotes: 3

Views: 171

Answers (1)

Phisn
Phisn

Reputation: 881

The problem you tried to represent is that someTable.key gives a different result than someTable["key"] but this cant be possible:

But it's so common to use string constants as keys there's a special shortcut syntax for it:

> t = {}
> t.foo = 123 -- same as t["foo"] (but not t[foo], which would use the variable foo as the key)
> = t.foo
123
> = t["foo"]
123

The shortcut syntax is only valid if the string consists of underscores, letters, and numbers, but shouldn't start with a number. (http://lua-users.org/wiki/TablesTutorial)

Supported by the fact that it works when not used in loadstring, I suspect that your problem is rather with Player(cid) player:getId() or "player:getPosition()". Important to notice that you are accessing player at two different times. 1. Directly as player:getId() and 2. though loadstring / pcall. The last possibility would be the Player(cid). One of them is propably not correctly initialized / declared.

I think because of different test conditions your second attempt local param = "print( #Game['getHouses']() )" worked.

Upvotes: 6

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