+ If you are using GameMaker Studio 2 or an Early Access version of GameMaker: Studio 1, you can have Lua directly read and write variables on GameMaker instances.
+
+ To do so, you would add three scripts to your project:
+
+/// ref_variable_instance_get(context, name)
+var q = argument0, s = argument1;
+with (q) return variable_instance_get(id, s);
+if (q < 100000) {
+ lua_show_error("Couldn't find any instances of " + string(q)
+ + " (" + object_get_name(q) + ")");
+} else lua_show_error("Couldn't find instance " + string(q));
+return undefined;
+(reads a variable from an instance),
+
+/// ref_variable_instance_set(context, name, value)
+var q = argument0, s = argument1, v = argument2, n = 0;
+with (q) { variable_instance_set(id, s, v); n++; }
+if (n) exit;
+if (q < 100000) {
+ lua_show_error("Couldn't find any instances of " + string(q)
+ + " (" + object_get_name(q) + ")");
+} else lua_show_error("Couldn't find instance " + string(q));
+(writes a variable to an instance(s)),
+
+/// ref_variable_instance_init(lua_state)
+var q = argument0;
+lua_add_function(q, "variable_instance_get", ref_variable_instance_get);
+lua_add_function(q, "variable_instance_set", ref_variable_instance_set);
+lua_add_code(q, '-- ref_variable_instance_init()
+ __idfields = __idfields or { };
+ debug.setmetatable(0, {
+ __index = function(self, name)
+ if (__idfields[name]) then
+ return _G[name];
+ else
+ return variable_instance_get(self, name);
+ end
+ end,
+ __newindex = variable_instance_set,
+ })
+');
+(exposes the above scripts to a Lua state and sets it up to use them when trying to read/write a field on a numeric value (id)).
+
+ Then you can use them as following:
+
+// create a Lua state:
+state = lua_state_create();
+// allow the state to work with GM instances:
+ref_variable_instance_init(state);
+// add a test function to the state -
+// function takes an instance and modifies it's `result` variable.
+lua_add_code(state, "function test(q) q.result = 'Hello!' end");
+// call the test-function for the current instance and display the result:
+result = "";
+lua_call(state, "test", id);
+show_debug_message(result);
+