在运行时使用C ++中使用的脚本语言创建新的类/成员 [英] Creating new classes/members at run-time in scripting languages used in C++
问题描述
我已经不停地解决这个问题了几个月，现在想真正提出一个合适的解决方案，以解决使用以下方法创建新的用户定义类(以及这些类的实例)的情况C ++ 11项目中运行时的成员函数/属性.
I've been working on this problem off and on for a few months, and now wanted to really come up with a proper solution that will handle the case of creating new user-defined classes (and instances of those classes) with member functions/properties at run-time in a C++11 project.
到目前为止，我一直在使用SWIG(以前使用Python，现在使用Lua探索Squirrel).就像到目前为止我所遇到的所有C ++绑定/嵌入库(Luna *，luabinder，luabind，OOLAa，Sqrat/Sqext，Squall)一样，所有人都希望您的类在执行代码之前就已在C ++中进行了预定义，因为它们要么依赖于预处理器，要么依赖于预处理器.指令或模板.
So far, I've been using SWIG (formerly with Python, now with Lua, exploring Squirrel). Like all the C++ binding/embedding libraries I've encountered so far (Luna*, luabinder, luabind, OOLua, Sqrat/Sqext, Squall), all expect your classes to be predefined in C++ prior to code execution because they either rely on preprocessor directives or templates.
所以我的问题是，有没有使用更程序化的方法来包装语言的库，或者对于Lua或Squirrel之类的东西有很好的教程/示例，有人会建议他们处理自定义的创建自定义成员和函数的命名类?某些方向将不胜感激.
So my question is, are there any libraries out there that use a more procedural approach to wrapping a language, or are there any good tutorials/examples for something like Lua or Squirrel, that one would recommend for handling the creation of custom-named classes with custom members and functions? Some direction would be greatly appreciated.
即使只是一个很好的示例，它展示了如何在Lua，Squirrel中通过各自的C ++ API在不使用宏/模板/动态生成的代码的情况下在Lua，Squirrel中创建具有函数和属性的自定义类，也将大有帮助.
Even simply a good example showing how to create a custom class with a function and a property, in either Lua, Squirrel, via their respective C++ APIs without the use of macros/templates/dynamically-generated code, would be hugely helpful.
我所做的只是创建一个Instance类，该类包含成员键/值对的std::vector和一个成员，该成员标识类型，以便可以查找功能.但是，关于在Lua/Squirrel中创建简单类而不使用静态代码的文献很少.
I have gone as far as creating an Instance class that contains a std::vector of members key/value pairs, and a member identifying the type so functions can be looked up. However, there is very little documentation out there on creating simple classes in Lua/Squirrel without the use of static code.
我想要一个可以在任何平台上运行且无需动态链接的解决方案.
EDIT 2: I would like a solution that works on any platform and without having to dynamically link.
推荐答案
考虑以下Lua多重地图示例.
Consider following Lua multimap example.
Multimap = {};
function Multimap:__index(key)
if (key == 'keys') then
local ret = {}
for k,_ in pairs(self) do
ret[#ret+1] = k;
end
return ret;
else
return rawget(getmetatable(self), key)
end
end
function Multimap.Create()
local self = {};
setmetatable(self, Multimap);
return self;
end
function Multimap:Insert(key, value)
local list = self[key];
if (list == nil) then
list = {};
self[key] = list;
end
table.insert(list, value);
end
function Multimap:Remove(key, value)
local list = self[key];
assert(list ~= nil, "key not found");
for i = 1,#list do
if (list[i] == value) then
table.remove(list, i);
if (#list == 0) then
self[key] = nil;
end
return;
end
end
error("value not found");
end
-- testing
m = Multimap.Create()
m:Insert(1,5)
m:Insert(2,6)
m:Insert(3,7)
m:Insert(1,8)
m:Remove(2,6)
print(pcall(function()
m:Remove(2,6) -- will produce assert exception
end))
print("keys left: ", table.concat(m.keys, ','))
您可以通过C ++的几种方式来实现它.
You can implement this in C++ in several ways.
- 使用沉重的Lua API.下面的代码几乎与Lua完全一样.
#include <Lua/src/lua.hpp>
int Multimap_Index(lua_State* L) {
lua_settop(L, 2); // force 2 arguments
const char *key_value = "key";
size_t key_len;
const char *key = lua_tolstring(L, 2, &key_len);
if (!strncmp(key, key_value, strlen(key_value))) {
int i = 0;
lua_newtable(L); // stack : self, key, ret = {}
int ret = lua_gettop(L);
lua_pushnil(L); // stack : self, key, ret, nil
while (lua_next(L, 1) != 0) { // stack : self, key, ret, k, v
lua_pop(L, 1); // stack : self, key, ret, k
lua_len(L, ret); // stack : self, key, ret, k, #ret
lua_pushvalue(L, -2); // stack : self, key, ret, k, #ret, k
lua_rawseti(L, ret, lua_tointeger(L, -2)+1); // ret[#ret+1] = k ; || stack : self, key, ret, k, #ret
lua_pop(L, 1); // stack : self, key, ret, k
}
// stack : self, key, ret
return 1;
}
else {
lua_getmetatable(L, 1); // stack : self, key, metatable(self)
lua_pushvalue(L, 2); // stack : self, key, metatable(self), key
lua_rawget(L, -2); // stack : self, key, metatable(self), rawget(metatable(self), key)
return 1;
}
}
int Multimap_Remove(lua_State* L) {
lua_settop(L, 3); // force 3 arguments: self, key, value
lua_checkstack(L, 12); // reserve 12 arguments on stack (just in case)
lua_pushvalue(L, 2); // stack: self, key, value, key
lua_gettable(L, 1); // stack: self, key, value, list = self[key]
if (lua_isnil(L, -1))
luaL_error(L, "key not found");
lua_len(L, -1); // stack: self, key, value, list, #list
int count = lua_tointeger(L, -1);
lua_pop(L, 1); // stack: self, key, value, list
for (int i = 1; i <= count; ++i) {
lua_rawgeti(L, -1, i); // stack: self, key, value, list, v = list[i]
if (lua_compare(L, 3, 5, LUA_OPEQ)) { // if (list[i] == value)
lua_getglobal(L, "table"); // stack : self, key, value, list, v, table
lua_getfield(L, -1, "remove"); // stack : self, key, value, list, v, table, table.remove
lua_pushvalue(L, 4);
lua_pushinteger(L, i); // stack : self, key, value, list, v, table, table.remove, list, i
lua_call(L, 2, 0); // table.remove(list, i); || stack : self, key, value, list, v, table
lua_pushnil(L);
if (lua_next(L, 4) == 0) { // if list is empty table
lua_pushvalue(L, 2);
lua_pushnil(L);
lua_settable(L, 1); // self[key] = nil
}
return 0;
}
}
luaL_error(L, "value not found");
}
int main() {
auto L = luaL_newstate();
luaL_openlibs(L);
lua_newtable(L);
int Multimap = lua_gettop(L); // Multimap = {}
lua_pushvalue(L, Multimap);
lua_setglobal(L, "Multimap"); // _G.Multimap = Multimap;
// option 1: create a C function for operation
// Multimap.__index = &Multimap_Index
lua_pushcfunction(L, Multimap_Index);
lua_setfield(L, Multimap, "__index");
// option 2: compile Lua code and use it
luaL_loadstring(L,
"local self = {};\n"
"setmetatable(self, Multimap);\n"
"return self;\n"
);
lua_setfield(L, Multimap, "Create"); // Multimap.Create = &Multimap_Create
luaL_loadstring(L,
"local self, key, value = ...;\n" // initialize local variables from parameters here
"local list = self[key];\n"
"if (list == nil) then\n"
" list = {};\n"
" self[key] = list;\n"
"end\n"
"table.insert(list, value);\n"
);
lua_setfield(L, Multimap, "Insert"); // Multimap.Create = &Multimap_Insert
lua_pushcfunction(L, Multimap_Remove);
lua_setfield(L, Multimap, "Remove"); // Multimap.Create = &Multimap_Remove
lua_getfield(L, Multimap, "Create");
lua_call(L, 0, 1);
int m = lua_gettop(L);
lua_getfield(L, m, "Insert"); // stack : m, m.insert
int Insert = lua_gettop(L);
// m.Insert(m, 1, 5)
lua_pushvalue(L, Insert);
lua_pushvalue(L, m);
lua_pushinteger(L, 1);
lua_pushinteger(L, 5);
lua_call(L, 3, 0);
// m.Insert(m, 2, 6)
lua_pushvalue(L, Insert);
lua_pushvalue(L, m);
lua_pushinteger(L, 2);
lua_pushinteger(L, 6);
lua_call(L, 3, 0);
// m.Insert(m, 3, 7)
lua_pushvalue(L, Insert);
lua_pushvalue(L, m);
lua_pushinteger(L, 3);
lua_pushinteger(L, 7);
lua_call(L, 3, 0);
// m.Insert(m, 1, 8)
lua_pushvalue(L, Insert);
lua_pushvalue(L, m);
lua_pushinteger(L, 1);
lua_pushinteger(L, 8);
lua_call(L, 3, 0);
// m.Remove(m, 2, 6)
lua_getfield(L, m, "Remove");
lua_pushvalue(L, m);
lua_pushinteger(L, 2);
lua_pushinteger(L, 6);
lua_call(L, 3, 0);
// m.Remove(m, 2, 6)
lua_getfield(L, m, "Remove");
lua_pushvalue(L, m);
lua_pushinteger(L, 2);
lua_pushinteger(L, 6);
lua_pcall(L, 3, 0, 0);
printf("%s\n", lua_tostring(L, -1));
lua_getglobal(L, "table");
lua_getfield(L, -1, "concat");
lua_getfield(L, m, "keys");
lua_pushstring(L, ",");
lua_call(L, 2, 1);
printf("keys left: %s\n", lua_tostring(L, -1));
lua_close(L);
return 0;
}
- 或者您可以使用使用std :: multimap的Lua用户数据(我需要再花一个小时来实现这一点，所以请问您是否真的需要-但这不是您的问题所致)
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