Creating Ruby objects from C

ruby-talk
1

The following snippet of C code shows my attempt to create a Ruby string object by invoking the "new" method on the Ruby String class. I know it would be easier to do this using the rb_str_new or rb_str_new2 functions. However, I'm trying to understand how to create arbitrary Ruby objects from C using the "new" method. Can you spot what's wrong with this code?

   ID class_id = rb_intern("String");
   VALUE stringClass = rb_const_get(rb_cClass, class_id); // wrong 1st parameter?

   ID method_id = rb_intern("new");
   VALUE s1 = rb_funcall(stringClass, method_id, 1, "test");
   printf("s1 = %s!\n", RSTRING(s1)->ptr);

2

I think I found the answer. Using rb_class_new_instance works and is much simpler that what I was attempting.

···

On Mar 10, 2007, at 11:11 PM, Mark Volkmann wrote:

The following snippet of C code shows my attempt to create a Ruby string object by invoking the "new" method on the Ruby String class. I know it would be easier to do this using the rb_str_new or rb_str_new2 functions. However, I'm trying to understand how to create arbitrary Ruby objects from C using the "new" method. Can you spot what's wrong with this code?

  ID class_id = rb_intern("String");
  VALUE stringClass = rb_const_get(rb_cClass, class_id); // wrong 1st parameter?

  ID method_id = rb_intern("new");
  VALUE s1 = rb_funcall(stringClass, method_id, 1, "test");
  printf("s1 = %s!\n", RSTRING(s1)->ptr);

3

require 'rubygems'
require 'inline'

class X
   def initialize
     puts "blah"
   end
end

class Y
   inline do |builder|
     builder.c '
       VALUE blah() {
         return rb_funcall(rb_path2class("X"), rb_intern("new"), 0);
       }'
   end
end

p Y.new.blah

# % ./blah.rb
# blah
# #<X:0x1090ec4>

···

On Mar 10, 2007, at 9:11 PM, Mark Volkmann wrote:

The following snippet of C code shows my attempt to create a Ruby string object by invoking the "new" method on the Ruby String class. I know it would be easier to do this using the rb_str_new or rb_str_new2 functions. However, I'm trying to understand how to create arbitrary Ruby objects from C using the "new" method. Can you spot what's wrong with this code?