C extension, classes and subclasses

Ruby
1

I have a few doubts about how the init mechanism in ruby1.9 (I’m
working with it right now) works. I have a some classes and
subclasses, all defined inside a ruby extension, the base class
defines it’s +new+ method like this:

rb_define_singleton_method(rb_cMyClass, “new”, rb_cMyClass_s_new, -1);

This is the +new+ method:

VALUE rb_cMyClass_s_new(int argc, VALUE *argv, VALUE klass) {
void *node;
my_struct *ptr;
…
VALUE obj = Data_Make_Struct(klass, my_struct, 0, custom_free, ptr);
rb_obj_call_init(obj, argc, argv);
return obj;
}

and every subclass defines a +new+ method just like that. The thing is:
Does rb_obj_call_init calls the superclass’ new method?
Is this The Right Way™ to define/initialise classes and subclasses?

Thanks!

2

and every subclass defines a +new+ method just like that. The thing is:

not if it’s been redefined by the child class, I don’t think.

Does rb_obj_call_init calls the superclass’ new method?
Is this The Right Way™ to define/initialise classes and subclasses?

I think so. Try it out and see if it works :slight_smile:
=r [maybe asking core might be helpful, too, though…maybe not].

3

Hi,

On Fri, Jul 10, 2009 at 1:42 AM, Rolando A.[email protected]
wrote:

I have a few doubts about how the init mechanism in ruby1.9 (I’m working
with it right now) works. I have a some classes and subclasses, all defined
inside a ruby extension, the base class defines it’s +new+ method like this:

rb_define_singleton_method(rb_cMyClass, “new”, rb_cMyClass_s_new, -1);

Defining a singleton method “new” is old style which had been used for
ruby 1.6 or before.

Does rb_obj_call_init calls the superclass’ new method?

No, rb_obj_call_init just calls the instance method ‘initialize’.

Is this The Right Way™ to define/initialise classes and subclasses?

  1. Register a function to allocate a memory region by
    rb_define_alloc_func(rb_cMyClass, …).
  2. Define “initialize” method to initialize the memory region by
    rb_define_method(rb_cMyClass, “initialize”, …).
    It is called by MyClass.new after allocating the memory.
  3. Define “initialize_copy” method also for MyClass#dup and
    MyClass#clone. They don’t call “initialize”.