问在C中存储对Lua值的引用，该怎么做呢？
EN

Stack Overflow用户

提问于 2012-08-19 03:14:55

回答 1查看 248关注 0票数 4

例如，假设我有一个键处理接口，在C++中定义为：

class KeyBoardHandler 
{ 
public:
    virtual onKeyPressed(const KeyEventArgs& e);
    virtual onKeyReleased(const KeyEventArgs& e);
}

现在，我想将其扩展到Lua，以允许Lua利用并在脚本中注册KeyboardHandler。

这是到目前为止的原型。

class ScriptKeyboardHandler : public KeyboardHandler
{
public:
    ... previous methods omitted
    static void createFromScript(lua_State* L);
    bool createCppData();

private:
    ScriptKeyBoardHandler(lua_State* L);

    int mSelf;
    int mKeyPressFunc;
    int mKeyReleaseFunc;
    lua_State* mpLuaState;
}

现在，我知道实现会是这样的：

ScriptKeyboardHandler::ScriptKeyboardHandler(lua_State* L) :
    mpState(L)
{ }

ScriptKeyboardHandler::onKeyPressed(...) { 
     // check if mKeyPressFunc is a function
     // call it, passing in mself, and the event args as params
} 

// On Key Release omitted because being similar to the key pressed

ScriptKeyboardHandler::createFromScript(lua_State* L)
{
    auto scriptKeyboardHandler = new ScriptKeyboardHandler(L);
    if (scriptKeyboardHandler->createCppData())
    {
        // set the light user data and return a reference to ourself (mSelf)
    }
}

ScriptKeyboardHandler::createCppData() 
{
    // get the constructor data (second param) and find the keyPressed and keyReleased function, store those for later usage
    // any other data within the constructor data will apply to object
}

-- Syntax of the lua code
MyScriptHandler = { }
MyScriptHandler.__index = MyScriptHandler

MyScriptHandler.onKeyPress = function(self, args)
end

handler = createScriptHandler(handler, MyScriptHandler)
registerKeyHandler(handler)

我只是不知道当函数作为参数传递到表中时如何查找它们。

我这样做对吗？我希望我是，因为tolua不容易支持虚拟类，不能从脚本中派生出来，所以这一直是一个痛苦的问题。

我不担心其他函数，只是我如何从C代码中找到这些变量(按键函数等

lua

c++

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回答 1

Stack Overflow用户

回答已采纳

发布于 2012-08-19 03:36:59

下面是我的onKeyPressed实现的大致情况。

void ScriptKeyboardHandler::onKeyPressed()
{
   //Get the table corresponding to this object from the C registry
   lua_pushlightuserdata(mpLuaState, this);
   lua_gettable(mpLuaState,LUA_REGISTRYINDEX);

   //Now get the function to call from the object
   lua_pushstring(mpLuaState,"onKeyPress");
   lua_gettable(mpLuaState,-2);

   //Now call the function 
   lua_pushvalue(mpLuaState, -2 ); // Duplicate the self table as first argument
   //TODO: Add the other arguments
   lua_pcall(mpLuaState, 1, 0, 0 ); // TODO: You'll need some error checking here and change the 1 to represent the number of args.

   lua_pop(mpLuaState,1); //Clean up the stack

}