lua - 自引用用户数据和垃圾回收

Question

因为我的userdata对象引用了它们自己，所以我需要删除和设置一个变量以使垃圾回收器正常工作。

Lua代码：

obj = object:new()
-- 
-- Some time later
obj:delete()  -- Removes the self reference
obj = nil     -- Ready for collection

C代码：

typedef struct {
    int self; // Reference to the object
    int callback; // Reference to a Lua function
    // Other members and function references removed
} Object;

// Called from Lua to create a new object
static int object_new( lua_State *L ) {
    Object *obj = lua_newuserdata( L, sizeof( Object ) );

    // Create the 'self' reference, userdata is on the stack top
    obj->self = luaL_ref( L, LUA_REGISTRYINDEX );

    // Put the userdata back on the stack before returning
    lua_rawgeti( L, LUA_REGISTRYINDEX, obj->self );

    // The object pointer is also stored outside of Lua for processing in C

    return 1;
}

// Called by Lua to delete an object
static int object_delete( lua_State *L ) {
    Object *obj = lua_touserdata( L, 1 );

    // Remove the objects self reference
    luaL_unref( L, LUA_REGISTRYINDEX, obj->self );

    return 0;
}

// Called from Lua to set a callback function
static int object_set_callback( lua_State *L ) {
    Object *obj = lua_touserdata( L, 1 );

    // Unref an existing callbacks
    if ( obj->callback != 0 ) {
        luaL_unref( L, LUA_REGISTRYINDEX, obj->callback );
        obj->callback = 0;
    }

    // Set the new callback - function is on top of the stack
    obj->callback = luaL_ref( L, LUA_REGISTRYINDEX );
}

// Called from C to call a Lua function for the obj
static void do_callback( Object *obj ) {
    // Push the Lua function onto the stack
    lua_rawgeti( L, LUA_REGISTRYINDEX, obj->callback );

    // Push the userdata onto the stack
    lua_rawgeti( L, LUA_REGISTRYINDEX, obj->self );

    // Call the function
    lua_call( L, 1, 0 );
}

有什么办法可以在Lua中将对象设置为nil，并自动调用delete（）方法？或者，删除方法是否可以将所有引用该对象的变量设为零？自我参照能否被“弱化”？

编辑1：我已经包含了代码，以显示为什么对象引用自身；请参阅do_callback函数。每个对象都是树状结构的一部分，大部分处理工作都是用C语言完成的，但是用户可以设置一个自定义Lua函数，该函数在某些条件下会被调用。

编辑2：想到另一个可能的解决方案；当需要将对象的地址作为键传递给Lua时，是否可以在全局索引中查找对象，而不是每个obj都对其自身进行引用？

Answer 1

您可以尝试在注册表中创建一个弱表并在其中存储您的引用，这样将对象的所有引用设置为nil即可使其可用于gc。