Thank you, your translation really helped. Sorry about some of my remarks ... I am not a C programmer (although Ido know C) and all this looks a little foreign to me. I don't even know how to use GTK, but I want to learn how, and my way oflearning is bottom-up, that's why I started with GLib, although that'snot the recommended path of a newbie. All things are clearer since yesterday, and I'm slowly getting used tothe syntax. I'm not scared because it is baroque, I'm scared becausethere are things that I do not understand how they work ... but I'llfigure it out. Thanks again, On Sun, 2006-08-06 at 02:51 +0200, David Nečas (Yeti) wrote:> On Sun, Aug 06, 2006 at 02:11:51AM +0300, Alex Nedelcu wrote:> > I am trying to wrap my head around the GObject/GType system, but because> > of the lack of good documentation I am having trouble understanding it.> > > > Do you know any good tutorial on GObject ?> > I found the tutorial available on developer.gnome.org> > (http://www.le-hacker.org/papers/gobject/) not for newbies.> > The tutorial is now a part of GObject API documentation --> and it is good if you ask. In fact I cannot imagine what do> you mean by the `lack of good documentation'.> > > So I figured that the best way to understand anything is too have a> > working equivalent of something I can understand.> > In my opinion to understand GObject one should forget the> object oriented mumbo jumbo for a while and view both> classes and instances and the plain C structs they> physically are and how they contain their parents like> a matryoshka. That is to imagine what> > struct _Child {> Parent parent_instance;> > gint data_member;> };> > and> > struct _ChildClass {> ParentClass parent_class;> > void (*method)(Child *child);> };> > actually means. How [almost] everything else works clearly> follows from that. The syntax is kind of baroque but a user> of Gtk+ should be already trained to it.> > > Can someone be kind and translate the following Java classes in C using> > GObject ?> > > > (I am guessing that it should be a trivial task for someone experienced> > with the GObject system)> > > > Thanks in advance ...> > I'm leaving out the boilerplate, it is well described in the> tutorial and it adds lots of code to read without any value> (I doubt I have ever written it manually, I just take it> from anotehr file and use s/// to change names). I'm also> prefixing everything with my- (which is how namespaces are> made in C).> > Also see Gtk+ source code -- Gtk+ is nothing more than> a large collection of GObject examples...> > > > > abstract class Animal> > {> > void feed()> > {> > print("Feeding some animal");> > }> > }> > myanimal.h ================================================> > struct _MyAnimalClass {> GObjectClass parent_class;> > void (*feed)(MyAnimal *animal);> };> > struct _MyAnimal {> GObject parent_instance;> > /* empty */> };> > > void my_animal_feed(MyAnimal *animal);> > > myanimal.c ================================================> > static void my_animal_feed_real(MyAnimal *animal);> > G_DEFINE_ABSTRACT_TYPE(MyAnimal, my_animal, G_TYPE_OBJECT)> > static void> my_animal_class_init(MyAnimalClass *klass)> {> klass->feed = &my_animal_feed_real;> }> > static void> my_animal_init(MyAnimal *animal)> {> /* empty */> }> > void> my_animal_feed(MyAnimal *animal)> {> /* Generally the method must be tested for NULL, but> * here we know it always exists */> MY_ANIMAL_GET_CLASS(animal)->feed(animal);> }> > static void> my_animal_feed_real(MyAnimal *animal)> {> printf("Feeding some animal\n");> }> > > class Dog extends Animal> > {> > static int legs = 4;> > > > String name;> > int age;> > > > public Dog(String name, int age)> > {> > this.name = name;> > this.age = age;> > }> > > > void feed()> > {> > print("Feeding a canine named " + this.name);> > }> > }> > mydog.h ================================================> > struct _MyDogClass {> MyAnimalClass parent_class;> > gint legs;> };> > struct _MyDog {> MyAnimal parent_instance;> > GString *name;> gint age;> }> > MyDog* my_dog_new(const gchar *name, gint age);> > > mydog.c ================================================> > static void my_dog_finalize(GObject *object);> static void my_dog_feed(MyAnimal *animal);> > G_DEFINE_TYPE(MyDog, my_dog, MY_TYPE_DOG)> > static void> my_dog_class_init(MyDogClass *klass)> {> GObjectClass gobject_class = G_OBJECT_CLASS(klass);> MyAnimalClass animal_class = MY_ANIMAL_CLASS(klass);> > gobject_class->finalize = &my_dog_finalize;> animal_class->feed = &my_dog_feed;> /* The semantics is not exactly the same */> klass->legs = 4;> }> > static void> my_dog_init(MyDog *dog)> {> dog->name = g_string_new("");> }> > static void> my_dog_finalize(GObject *object)> {> MyDog *dog;> > dog = MY_DOG(object);> g_string_free(dog->name, TRUE);> > /* Generally the method must be tested for NULL, but> * here we know it always exists */> G_OBJECT_CLASS(my_dog_parent_class)->finalize(object);> }> > MyDog*> my_dog_new(const gchar *name,> gint age)> {> MyDog *dog;> > dog = g_object_new(MY_TYPE_DOG, NULL);> g_string_assign(dog->name, name);> dog->age = age;> /* If MyDog registered name and age as properties we> * could also do> * dog = g_object_new(MY_TYPE_DOG, "name", name, "age", age, NULL);> */> > return dog;> }> > static void> my_dog_feed(MyAnimal *animal)> {> MyDog *dog;> > dog = MY_DOG(animal);> printf("Feeding a canine named %s\n", dog->name->str);> }> > > // .......> > > > Animal animals[] = {> > new Dog("Bella", 2),> > new Dog("Toto", 3)> > };> > > > for (int i=0; i<animals.length; i++)> > animals[i].feed();> > /* The array initialization above is too dynamic plain> * old C, so just make two animals to demonstrate feed().> *> * Also, it is impossible to work with GObjects by _value_,> * use pointers. */> > static MyAnimal *animals[2];> > animals[0] = MY_ANIMAL(my_dog_new("Bella", 2));> animals[1] = MY_ANIMAL(my_dog_new("Toto", 3));> > for (i = 0; i < G_N_ELEMENTS(animals); i++)> my_animal_feed(animals[i]);> > > Yeti> > > --> Anonyms eat their boogers.> _______________________________________________> > gtk-list@xxxxxxxxx> http://mail.gnome.org/mailman/listinfo/gtk-list _______________________________________________gtk-list@xxxxxxxxxxxxx://mail.gnome.org/mailman/listinfo/gtk-list
