From: Sean O'Dell <sean@...>
Date: 2004-06-23T04:59:39+09:00
Subject: Re: passing a block in an extension

On Tuesday 22 June 2004 11:22, Charles Mills wrote:
> I am trying to write a function in C which calls a Ruby function using
> the block it was passed when called from Ruby.  Below is broken way to
> do it, but it explains the idea better.
>
> $ irb
> irb(main):001:0> require 'test'
> => true
> irb> my_method do |r|
> irb* 	puts r
> irb> end
> LocalJumpError: no block given
>          from (irb):4:in `each'
>          from (irb):4:in `my_method'
>          from (irb):4
> irb> exit
> $ more test.c
> #include <ruby.h>
> #include <intern.h>
>
> VALUE
> my_method(VALUE kernel)
> {
>          VALUE ary = rb_ary_new();
>          VALUE str1 = rb_str_new2("hey");
>          VALUE str2 = rb_str_new2("hey you");
>          rb_ary_push(ary, str1);
>          rb_ary_push(ary, str2);
>
>          return rb_funcall(ary, rb_intern("each"), 0, 0);
> }
>
> void Init_test()
> {
>          rb_define_module_function(rb_mKernel, "my_method", my_method,
> 0);
> }

Look at rb_scan_args in http://www.rubycentral.com/book/ext_ruby.html.

VALUE my_method(int argc, VALUE *argv, VALUE self)
{
    VALUE block = Qnil;
    VALUE ary = rb_ary_new();
    VALUE str1 = rb_str_new2("hey");
    VALUE str2 = rb_str_new2("hey you");

    rb_scan_args(argc, argv, "&", &block);

    rb_ary_push(ary, str1);
    rb_ary_push(ary, str2);

    return rb_funcall(ary, rb_intern("each"), 1, block);
}

rb_define_method(rb_cKernel, "my_method", my_method, -1);


I'm sure this code won't work right out of the gate, but it should be close to 
what you're after.

	Sean O'Dell