Using a static functions in a module

joakim

Hi, I'd like to know if it's possible to create a c++ module with static functions that I can call from any scene in my game. I could achieve the same functionality creating an instance in an autoloaded global script, but then I have to write get_node("/root/globals/").get_my_instance.function() everywhere. Of course I'd only save a few characters but I'm more interested if this is possible, and if not why. My minimal non-working example is below:

/* mystaticmodule.h */ #ifndef MYSTATICMODUDE_H #define MYSTATICMODULE_H #include "object.h" class mystaticmodule : public Object {   OBJ_TYPE(mystaticmodule, Object); protected:     static void _bind_methods();     public:     static int get_int(); }; #endif /* mystaticmodule.cpp */ #include "mystaticmodule.h" void _bind_methods() {   ObjectTypeDB::bind_method("get_int",&mystaticmodule::get_int); } int mystaticmodule::get_int() {   return 42; }

compiling (on ubuntu: scons platform=x11) yields following errors:

g++ -o modules/mystaticmodule/mystaticmodule.x11.tools.64.o -c -g2 -Wall -DDEBUG_ENABLED -DDEBUG_MEMORY_ENABLED -DFREETYPE_ENABLED -DOC_X86_ASM -DDEBUG_MEMORY_ALLOC -DSCI_NAMESPACE -DENABLE_DEPRECATED -DOPENGL_ENABLED -DALSA_ENABLED -DJOYDEV_ENABLED -DX11_ENABLED -DUNIX_ENABLED -DGLES2_ENABLED -DGLES_OVER_GL -DMUSEPACK_ENABLED -DSQUISH_ENABLED -DVORBIS_ENABLED -DOPUS_ENABLED -DTHEORA_ENABLED -DTHEORALIB_ENABLED -DPNG_ENABLED -DDDS_ENABLED -DPVR_ENABLED -DJPG_ENABLED -DWEBP_ENABLED -DSPEEX_ENABLED -DTOOLS_ENABLED -DGDSCRIPT_ENABLED -DMINIZIP_ENABLED -DXML_ENABLED -DETC1_ENABLED -DGLEW_ENABLED -DGLEW_STATIC -Icore -Icore/math -Itools -Idrivers -I. -Iplatform/x11 -I/usr/include/freetype2 -Imodules/mystaticmodule modules/mystaticmodule/mystaticmodule.cpp In file included from core/object.h:696:0,                  from modules/mystaticmodule/mystaticmodule.h:4,                  from modules/mystaticmodule/mystaticmodule.cpp:1: core/object_type_db.h: In instantiation of 'static MethodBind* ObjectTypeDB::bind_method(N, M) [with N = const char*; M = int (*)()]': modules/mystaticmodule/mystaticmodule.cpp:5:63:   required from here core/object_type_db.h:337:49: error: no matching function for call to 'create_method_bind(int (*&)())'    MethodBind *bind = create_method_bind(p_method);                                                  ^ core/object_type_db.h:337:49: note: candidates are: In file included from core/method_bind.h:346:0,                  from core/object_type_db.h:33,                  from core/object.h:696,                  from modules/mystaticmodule/mystaticmodule.h:4,                  from modules/mystaticmodule/mystaticmodule.cpp:1: core/method_bind.inc:68:13: note: template<class T> MethodBind* create_method_bind(void (T::*)())  MethodBind* create_method_bind( void (T::*p_method)()  ) ...

juan-linietsky

do not use a static function, and register a singleton:static mystaticmodule * module[..]module = memnew( mystaticmodule);Globals::get_singleton()->add_singleton( Globals::Singleton("MyStaticModule",module) );then delete module at exit. Access your function from script as:MyStaticModule.get_int()

joakim

Thanks Juan,I was reading about the use of singletons, but I have never used that concept before, I will give it a go. Maybe this is opening a can of worms but, in the context of Godot and making games, why is a singleton preferred to static methods? Is it due to the implementation or is there a more conceptual reason?

Dredok

Do you know what is a singleton in first place? Usually people misunderstand the concept, and use a singleton implementation only to have access to a global variable with lazy initialization...Using "static c++ methods" is not better neither worse than using singletons. It smells like a bad design, and seems you want to use a global variable, then use it. Neither a singleton or a static method is better or worse.If you are truly interested in writing large or reusable code, please try to not abuse globals, statics or singletons. The promote coupled code and in the end are hard to extend. Of course a simple game / app could be easily write using globals wihout any trouble, but do you a favor and try to avoid these patterns for serious / large projects

joakim

So I am making a procedurally generated RPG. I had started this as a pure c++ project but got tired of making an engine rather than a game and decided to use Godot. I had the code ready but the scene structure confused me. What I wanted to be global is the map generator which will be used to setup every scene and a Dice class used like Dice::roll(weapon.get_dice_type(),weapon.get_dice_n()) and used by all PC/NPC's and some misc game mechanics. For testing/debugging it is important to have them static/singleton so that I can set the PRN generator seed at init and have consistent results. In my c++ I could just include the Dice header and use a have Dice::type member variable for e.g a weapon class. This is why I wanted the class to be globally accessible. I realize now that I don't have to switch scenes that often I can just recreate the map in the current scene (I also just learned that you can have scenes within a scene, which recasts what I thought I scene was supposed to be). I think I should have separate scenes for menus, world map et.c so now I use these as singletons which works great.