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comp.lang.ruby

creating Ruby objects from C

R. Mark Volkmann

3/11/2007 5:11:00 AM

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 Answers

R. Mark Volkmann

3/11/2007 5:25:00 AM

0

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);

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

Ryan Davis

3/11/2007 8:37:00 PM

0


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?

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>