From: Bryan Richardson <btrichardson@...>
Date: 2008-05-06T21:49:51+09:00
Subject: Yet another question about extending ruby with C

Hello all,

I'm still working on figuring how how to extend ruby with C libraries.
Hope someone can help me with this one!

Say I have the following:

typedef struct {
  char* name;
} Foo;

static VALUE rb_cBar;
static VALUE rb_cTest;

static VALUE foo_new(VALUE self) {
  Foo* f;
  VALUE info;
  info = Data_Make_Struct(rb_cTest, Foo, 0, free, f);
  rb_obj_call_init(info, 0, 0);
  return info;
}

static VALUE foo_init(VALUE self) {
  VALUE str;
  char* name = "Bryan";
  str = rb_str_new2(name);
  rb_iv_set(self, "@name", str);
  return self;
}

static VALUE test(VALUE self, VALUE arg) {
  Foo* f;
  Data_Get_Struct(arg, Foo, f);
  printf("Name: %s\n", f->name);
  return Qnil;
}

void Init_power_flow() {
  rb_cBar = rb_define_class("Bar", rb_cObject);
  rb_cTest = rb_define_class("Test", rb_cObject);
  rb_define_method(rb_cBar, "test", test, 1);
  rb_define_method(rb_cBar, "new_foo", foo_new, 0);
  rb_defien_method(rb_cTest, "initialize", foo_init, 0);
}

If I do the following, everything works perfectly and I see my name
printed
on the screen:

b = Bar.new
f = b.new_foo
b.test(f)  // prints "Bryan"

However, say I change the foo_new method to be the following:

static VALUE foo_new(VALUE self) {
  Foo* f;
  VALUE info;
  f = ALLOC(Foo);
  f->name = "Bryan";
  info = Data_Wrap_Struct(self, 0, free, f);
  return info;
}

and I change the method declaration in Init to be the following:

rb_define_method(rb_cTest, "initialize", foo_new, 0);

Now, when I do what I did before, I get an error:

b = Bar.new
f = Test.new
b.test(f)  // TypeError: wrong argument type Test (expected Data)

Any idea why trying to define a constructor rather than a 'factory'
method is causing me issues?

--
Thanks in advance!
Bryan
-- 
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