GLib - difference between class_init and init class methods

Question

I'm a newbie with glib and I'm still struggling to understand the difference between my_class_name_class_init() methods and my_class_name_init() methods.

I get that the latter is kinda equivalent to a C++ constructor and that goes per-instance of the object created but I don't quite understand the purpose of those my_class_name_class_init() methods. By reading the documentation I think class_init() methods are somewhat similar to a static constructor valid for all instances but I'm still not sure I got this right.

What's the purpose of class_init() methods?

Answer 1

class_init functions are executed once per class, before first instance is constructed - in that way they are similar to C# static constructors. In contrast, instance_init functions are called for every instance of object created and are responsible for initializing that instance.

Like static constructors, class_init are responsible for initializing any shared data all instances might need, but more importantly, in GObject they play vital role in setting up GObject object system. They are responsible for:

• Setting up virtual function tables
• Setting up GObject property system
• Setting up signals