“错误:尝试调用nil值"尝试调用lua脚本时 [英] "Error: attempt to call a nil value" when trying to call lua script
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问题描述
我正在尝试从C ++调用lua函数，并且不断收到错误消息错误:尝试调用nil值".
lua函数创建一个C ++对象，然后调用其方法之一，该胶合代码已使用tolua ++生成.调用lua函数时，我传入了lua_State指针，因为C ++类的构造函数需要一个指针，而lua函数会将其交给该指针.
但是据我所知，它永远都不会运行，只是根本不运行脚本.至少该错误没有引用脚本中的任何行号.
这是调用该函数的C ++代码:
int main()
{
lua_State *lState;
lState = luaL_newstate(); //new lua state
tolua_TestClass_open (lState); //open libs for TestClass
int iStatus = luaL_loadfile( lState, "lua1.lua" ); //load script
if (iStatus)
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
iStatus = lua_pcall( lState, 0, 0, 0); //initialise the lua script
if( iStatus )
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
lua_getglobal( lState, "lua1Function" ); //starting the function call
lua_pushlightuserdata (lState, lState); //lState is also being passed in as a parameter
iStatus = lua_pcall( lState, 1, 0, 0 ); //calling on this lua state with 1 argument expecting 0 outputs
if( iStatus ) //error checking
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
return 1;
}
这是lua脚本:
function lua1Function(lstate)
tclass = TestClass:new();
tclass:method1();
tclass:method3();
end
我很确定这不像忘记做那么简单:
tclass = TestClass:new(lstate);
胶水代码似乎表明我不需要这样做，
/* method: new of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_new00
static int tolua_TestClass_TestClass_new00(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertable(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
lua_State* tolua_var_1 = tolua_S; //seems to know I want the lua_State by default,
//usually it will pop a usertype or luanumber or whatever off the stack,
//depending on the parameter
{
TestClass* tolua_ret = (TestClass*) Mtolua_new((TestClass)(tolua_var_1));
tolua_pushusertype(tolua_S,(void*)tolua_ret,"TestClass");
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'new'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
产生的错误消息似乎证实了我的理论:函数'new'中的错误.参数2是'userdata'；应该是'[no object]'". 也就是说，没想到/不需要我传递那个lua_State指针
我很茫然，我很难找到解决lua问题的解决方案，因为在涉及tolua ++方面，教程/文档似乎很薄，但是现在更改绑定库为时已晚. /p>
任何帮助将不胜感激，我希望我已经提供了足够的诊断问题的方法.
编辑:这是我的TestClass.cpp代码(您可能会忽略method1、2和3，因为似乎由于此错误而未调用它们):
#include "TestClass.h"
#include <iostream>
TestClass::TestClass(lua_State *L)
{
num = NULL;
lState = L;
}
int TestClass::method1()
{
int iStatus = luaL_loadfile( lState, "lua2.lua" );
if (iStatus)
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
iStatus = lua_pcall( lState, 0, 0, 0); //this might be to initialise the lua script
if( iStatus )
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
///////////call lua function, passing on self pointer onto the stack////////////////
lua_getglobal( lState, "lua2Function" );
tolua_pushusertype(lState, this, "TestClass");
iStatus = lua_pcall( lState, 1, 1, 0 );
if( iStatus ) //error checking
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
///////////lua function returns an int, return it////////////
num = lua_tointeger( lState, -1 );
return 0;
}
int TestClass::method2(int i)
{
i += 2;
return i;
}
void TestClass::method3()
{
std::cout << (char)num << std::endl;
}
/*
** Lua binding: TestClass
** Generated automatically by tolua++-1.0.92 on 04/05/11 17:59:24.
*/
#ifndef __cplusplus
#include "stdlib.h"
#endif
#include "string.h"
#include "tolua++.h"
/* function to release collected object via destructor */
#ifdef __cplusplus
static int tolua_collect_TestClass (lua_State* tolua_S)
{
TestClass* self = (TestClass*) tolua_tousertype(tolua_S,1,0);
Mtolua_delete(self);
return 0;
}
#endif
/* function to register type */
static void tolua_reg_types (lua_State* tolua_S)
{
tolua_usertype(tolua_S,"TestClass");
}
/* method: new of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_new00
static int tolua_TestClass_TestClass_new00(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertable(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
lua_State* tolua_var_1 = tolua_S;
{
TestClass* tolua_ret = (TestClass*) Mtolua_new((TestClass)(tolua_var_1));
tolua_pushusertype(tolua_S,(void*)tolua_ret,"TestClass");
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'new'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* method: new_local of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_new00_local
static int tolua_TestClass_TestClass_new00_local(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertable(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
lua_State* tolua_var_1 = tolua_S;
{
TestClass* tolua_ret = (TestClass*) Mtolua_new((TestClass)(tolua_var_1));
tolua_pushusertype(tolua_S,(void*)tolua_ret,"TestClass");
tolua_register_gc(tolua_S,lua_gettop(tolua_S));
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'new'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* method: method1 of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_method100
static int tolua_TestClass_TestClass_method100(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertype(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
TestClass* self = (TestClass*) tolua_tousertype(tolua_S,1,0);
#ifndef TOLUA_RELEASE
if (!self) tolua_error(tolua_S,"invalid 'self' in function 'method1'", NULL);
#endif
{
int tolua_ret = (int) self->method1();
tolua_pushnumber(tolua_S,(lua_Number)tolua_ret);
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'method1'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* method: method2 of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_method200
static int tolua_TestClass_TestClass_method200(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertype(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnumber(tolua_S,2,0,&tolua_err) ||
!tolua_isnoobj(tolua_S,3,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
TestClass* self = (TestClass*) tolua_tousertype(tolua_S,1,0);
int tolua_var_2 = ((int) tolua_tonumber(tolua_S,2,0));
#ifndef TOLUA_RELEASE
if (!self) tolua_error(tolua_S,"invalid 'self' in function 'method2'", NULL);
#endif
{
int tolua_ret = (int) self->method2(tolua_var_2);
tolua_pushnumber(tolua_S,(lua_Number)tolua_ret);
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'method2'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* method: method3 of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_method300
static int tolua_TestClass_TestClass_method300(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertype(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
TestClass* self = (TestClass*) tolua_tousertype(tolua_S,1,0);
#ifndef TOLUA_RELEASE
if (!self) tolua_error(tolua_S,"invalid 'self' in function 'method3'", NULL);
#endif
{
self->method3();
}
}
return 0;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'method3'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* Open function */
TOLUA_API int tolua_TestClass_open (lua_State* tolua_S)
{
tolua_open(tolua_S);
tolua_reg_types(tolua_S);
tolua_module(tolua_S,NULL,0);
tolua_beginmodule(tolua_S,NULL);
#ifdef __cplusplus
tolua_cclass(tolua_S,"TestClass","TestClass","",tolua_collect_TestClass);
#else
tolua_cclass(tolua_S,"TestClass","TestClass","",NULL);
#endif
tolua_beginmodule(tolua_S,"TestClass");
tolua_function(tolua_S,"new",tolua_TestClass_TestClass_new00);
tolua_function(tolua_S,"new_local",tolua_TestClass_TestClass_new00_local);
tolua_function(tolua_S,".call",tolua_TestClass_TestClass_new00_local);
tolua_function(tolua_S,"method1",tolua_TestClass_TestClass_method100);
tolua_function(tolua_S,"method2",tolua_TestClass_TestClass_method200);
tolua_function(tolua_S,"method3",tolua_TestClass_TestClass_method300);
tolua_endmodule(tolua_S);
tolua_endmodule(tolua_S);
return 1;
}
#if defined(LUA_VERSION_NUM) && LUA_VERSION_NUM >= 501
TOLUA_API int luaopen_TestClass (lua_State* tolua_S) {
return tolua_TestClass_open(tolua_S);
};
#endif
解决方案
原来，唯一的问题是脚本中的"lua2Function"是用小写的F拼写的.我粘贴的代码实际上运行良好.多么尴尬！
我想我已经了解到，至少tolua ++确实确实负责将lua_State指针传递给方法.
I'm trying to call a lua function from C++ and I keep getting the error message "Error: attempt to call a nil value".
The lua function creates a C++ object and then calls one of its methods, the glue code has been generated with tolua++. When calling the lua function I pass in a lua_State pointer, as the C++ class needs one for its constructor, which the lua function hands to it.
But as far as I can tell it never gets that far, it simply doesn't run the script at all. At least the error doesn't reference any line numbers in the script.
Here is the C++ code calling the function:
int main()
{
lua_State *lState;
lState = luaL_newstate(); //new lua state
tolua_TestClass_open (lState); //open libs for TestClass
int iStatus = luaL_loadfile( lState, "lua1.lua" ); //load script
if (iStatus)
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
iStatus = lua_pcall( lState, 0, 0, 0); //initialise the lua script
if( iStatus )
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
lua_getglobal( lState, "lua1Function" ); //starting the function call
lua_pushlightuserdata (lState, lState); //lState is also being passed in as a parameter
iStatus = lua_pcall( lState, 1, 0, 0 ); //calling on this lua state with 1 argument expecting 0 outputs
if( iStatus ) //error checking
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
return 1;
}
Here is the lua script:
function lua1Function(lstate)
tclass = TestClass:new();
tclass:method1();
tclass:method3();
end
I'm fairly sure it's not something as simple as forgetting to do:
tclass = TestClass:new(lstate);
As the glue code seems to indicate I don't need to do that, here:
/* method: new of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_new00
static int tolua_TestClass_TestClass_new00(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertable(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
lua_State* tolua_var_1 = tolua_S; //seems to know I want the lua_State by default,
//usually it will pop a usertype or luanumber or whatever off the stack,
//depending on the parameter
{
TestClass* tolua_ret = (TestClass*) Mtolua_new((TestClass)(tolua_var_1));
tolua_pushusertype(tolua_S,(void*)tolua_ret,"TestClass");
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'new'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
And the error message THAT produces seems to confirm my theory: "error in function 'new'. argument #2 is 'userdata'; '[no object]' expected." i.e. it wasn't expecting/doesn't need me to pass in that lua_State pointer
I'm at a loss, I have a lot of trouble finding solutions to problems with lua because tutorials/documentation seem to be pretty thin on the ground where tolua++ is concerned, but it's too late to change binding library now.
Any help would be much appreciated, I hope I've provided enough to diagnose the problem.
EDIT: Here's my TestClass.cpp code (you can probably ignore method1, 2 and 3 as they don't seem to be called because of this error):
#include "TestClass.h"
#include <iostream>
TestClass::TestClass(lua_State *L)
{
num = NULL;
lState = L;
}
int TestClass::method1()
{
int iStatus = luaL_loadfile( lState, "lua2.lua" );
if (iStatus)
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
iStatus = lua_pcall( lState, 0, 0, 0); //this might be to initialise the lua script
if( iStatus )
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
///////////call lua function, passing on self pointer onto the stack////////////////
lua_getglobal( lState, "lua2Function" );
tolua_pushusertype(lState, this, "TestClass");
iStatus = lua_pcall( lState, 1, 1, 0 );
if( iStatus ) //error checking
{
std::cout << "Error: " << lua_tostring( lState, -1 );
return 1;
}
///////////lua function returns an int, return it////////////
num = lua_tointeger( lState, -1 );
return 0;
}
int TestClass::method2(int i)
{
i += 2;
return i;
}
void TestClass::method3()
{
std::cout << (char)num << std::endl;
}
/*
** Lua binding: TestClass
** Generated automatically by tolua++-1.0.92 on 04/05/11 17:59:24.
*/
#ifndef __cplusplus
#include "stdlib.h"
#endif
#include "string.h"
#include "tolua++.h"
/* function to release collected object via destructor */
#ifdef __cplusplus
static int tolua_collect_TestClass (lua_State* tolua_S)
{
TestClass* self = (TestClass*) tolua_tousertype(tolua_S,1,0);
Mtolua_delete(self);
return 0;
}
#endif
/* function to register type */
static void tolua_reg_types (lua_State* tolua_S)
{
tolua_usertype(tolua_S,"TestClass");
}
/* method: new of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_new00
static int tolua_TestClass_TestClass_new00(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertable(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
lua_State* tolua_var_1 = tolua_S;
{
TestClass* tolua_ret = (TestClass*) Mtolua_new((TestClass)(tolua_var_1));
tolua_pushusertype(tolua_S,(void*)tolua_ret,"TestClass");
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'new'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* method: new_local of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_new00_local
static int tolua_TestClass_TestClass_new00_local(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertable(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
lua_State* tolua_var_1 = tolua_S;
{
TestClass* tolua_ret = (TestClass*) Mtolua_new((TestClass)(tolua_var_1));
tolua_pushusertype(tolua_S,(void*)tolua_ret,"TestClass");
tolua_register_gc(tolua_S,lua_gettop(tolua_S));
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'new'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* method: method1 of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_method100
static int tolua_TestClass_TestClass_method100(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertype(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
TestClass* self = (TestClass*) tolua_tousertype(tolua_S,1,0);
#ifndef TOLUA_RELEASE
if (!self) tolua_error(tolua_S,"invalid 'self' in function 'method1'", NULL);
#endif
{
int tolua_ret = (int) self->method1();
tolua_pushnumber(tolua_S,(lua_Number)tolua_ret);
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'method1'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* method: method2 of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_method200
static int tolua_TestClass_TestClass_method200(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertype(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnumber(tolua_S,2,0,&tolua_err) ||
!tolua_isnoobj(tolua_S,3,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
TestClass* self = (TestClass*) tolua_tousertype(tolua_S,1,0);
int tolua_var_2 = ((int) tolua_tonumber(tolua_S,2,0));
#ifndef TOLUA_RELEASE
if (!self) tolua_error(tolua_S,"invalid 'self' in function 'method2'", NULL);
#endif
{
int tolua_ret = (int) self->method2(tolua_var_2);
tolua_pushnumber(tolua_S,(lua_Number)tolua_ret);
}
}
return 1;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'method2'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* method: method3 of class TestClass */
#ifndef TOLUA_DISABLE_tolua_TestClass_TestClass_method300
static int tolua_TestClass_TestClass_method300(lua_State* tolua_S)
{
#ifndef TOLUA_RELEASE
tolua_Error tolua_err;
if (
!tolua_isusertype(tolua_S,1,"TestClass",0,&tolua_err) ||
!tolua_isnoobj(tolua_S,2,&tolua_err)
)
goto tolua_lerror;
else
#endif
{
TestClass* self = (TestClass*) tolua_tousertype(tolua_S,1,0);
#ifndef TOLUA_RELEASE
if (!self) tolua_error(tolua_S,"invalid 'self' in function 'method3'", NULL);
#endif
{
self->method3();
}
}
return 0;
#ifndef TOLUA_RELEASE
tolua_lerror:
tolua_error(tolua_S,"#ferror in function 'method3'.",&tolua_err);
return 0;
#endif
}
#endif //#ifndef TOLUA_DISABLE
/* Open function */
TOLUA_API int tolua_TestClass_open (lua_State* tolua_S)
{
tolua_open(tolua_S);
tolua_reg_types(tolua_S);
tolua_module(tolua_S,NULL,0);
tolua_beginmodule(tolua_S,NULL);
#ifdef __cplusplus
tolua_cclass(tolua_S,"TestClass","TestClass","",tolua_collect_TestClass);
#else
tolua_cclass(tolua_S,"TestClass","TestClass","",NULL);
#endif
tolua_beginmodule(tolua_S,"TestClass");
tolua_function(tolua_S,"new",tolua_TestClass_TestClass_new00);
tolua_function(tolua_S,"new_local",tolua_TestClass_TestClass_new00_local);
tolua_function(tolua_S,".call",tolua_TestClass_TestClass_new00_local);
tolua_function(tolua_S,"method1",tolua_TestClass_TestClass_method100);
tolua_function(tolua_S,"method2",tolua_TestClass_TestClass_method200);
tolua_function(tolua_S,"method3",tolua_TestClass_TestClass_method300);
tolua_endmodule(tolua_S);
tolua_endmodule(tolua_S);
return 1;
}
#if defined(LUA_VERSION_NUM) && LUA_VERSION_NUM >= 501
TOLUA_API int luaopen_TestClass (lua_State* tolua_S) {
return tolua_TestClass_open(tolua_S);
};
#endif
解决方案
It turns out the only problem was that "lua2Function" was spelt with a lower-case F in the script. The code as I've pasted it actually works fine. How thoroughly embarrassing!
I guess I've learnt that tolua++ definitely DOES take care of passing lua_State pointers into methods, at least.
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