Call C + + function instance _lua in Lua

So far, there should be some familiarity with the communication between LUA and C + +, and today we'll show you the last one.
(Narrator: What?) The last one? Is it over yet? That's great, ~!. ）

Previous Chapter Portal: http://www.jb51.net/article/55097.htm

1. Lua calls C + + functions

Lua to invoke C + + functions is quite convenient, first of all, we create a C + + function first:

Copy Code code as follows:

Public
static int getnumber (int num);
　　
　　
int hellolua::getnumber (int num) {
Cclog ("GetNumber num =%d", num);
return num + 1;
}

Class or something, I just ignored that directly on the function.
(Narrator: = = good lazy!) ）

This is a very simple function that gives a value that returns a value of +1.
Now, we want to call this function in Lua, we need to write one more function.
(Narrator: That, why the GetNumber function is static?) ）

Copy Code code as follows:

Public
static int Cpp_getnumber (lua_state* PL);

int Hellolua::cpp_getnumber (lua_state* pL) {
/* Take a value from the top of the stack * *
int num = (int) lua_tonumber (PL, 1);

/* Call the GetNumber function, the return value into the stack * *
Lua_pushnumber (PL, GetNumber (num));

/* Returns the number of values, GetNumber only one return value, so return 1 * * *
return 1;
}

(Narrator: It's static again!) ）
What the hell is going on here? We know that Lua and C + + can only communicate through the stack, so it's impossible for Lua to call the GetNumber function directly, so we set up a cpp_getnumber function as an intermediary.
Cpp_getnumber function has a lua_state* pl parameter, with this parameter, C + + will be able to take value from the LUA stack, the rest is very simple, do not want too much explanation ...

Let's just explain.
(Narrator: Your sister paper, I know!) ）

1 First, the LUA script will call the Cpp_getnumber function, and as for why it can be invoked, once explained, I know that the narrator will definitely ask. (Narrator: A feeling of inability to spit ... ）
2 when Cpp_getnumber is called, everything goes back to the operation of Lua in C + +, the top of the stack will store the parameters required by the function, take out to use on it.
3 after LUA calls Cpp_getnumber, you need a result, of course, the result can only be stored in the stack, so it is logical to put the results of getnumber into the stack.
4 Finally, Cpp_getnumber returns a value that is not the result of the function's execution, but rather the number of GetNumber needs to return (LUA supports multiple return values)
Narrator: Did you get it?
(Narrator: The amount ...). Don't understand)

Well, since everyone understands, I won't say more.
(Narrator: Your Sister paper's o O!) ）

2. The end of

Finally, the tutorial on Lua came to an end, and I wanted to write a luabind tutorial (very powerful!). ）。 However, writing a tutorial is a time-consuming task, 10 minutes to learn the knowledge, maybe I will take 2 hours to birth a tutorial. (Narrator: OK, so let's support him more ...)
 
However, it is not much of a challenge to take these 6 tutorials thoroughly and then develop them in cocos2d-x with Lua. (Better get to know Luabind)
Maybe, I'm going to go on to write the Lua tutorial, and now I'm going to continue to study cocos2d-x. Because of the tutorial (which has been writing the state machine tutorial and the LUA tutorial for two weeks), I've stopped for nearly two weeks. Must hurry up ~ cannot lag behind ~
So, I wish you a happy New Year's day.
(Narrator: Are you sure you will post this tutorial after New Year's Day?)
 
Then, I hope that everyone gently moving the mouse, click on the "top" ~ hehe