From: Daniel Berger <Daniel.Berger@...>
Date: 2006-08-29T01:41:18+09:00
Subject: instance_eval, yield, C extensions

Hi all,

How do I write the code below within a C extension?  I've seen a few threads 
about it (including ruby-talk: 86105) but I'm just not "getting it".

# Assume Foo is a subclass of String
module Kernel
    def my_meth
       instance_eval{ Foo.new(yield) }
    end
end

With that I can do my_meth{ "some_string" } and get back a String object.

I tried this:

static VALUE foo_block(VALUE self){
    return rb_funcall(cFoo, rb_intern("new"), 0, rb_yield(self));
}

static VALUE kernel_foo(VALUE self){
    VALUE v_proc = rb_proc_new(foo_block, self); /* Also tried Qnil */
    return rb_funcall(rb_cObject, rb_intern("instance_eval"), 0, v_proc);
}

rb_define_method(rb_mKernel, "my_meth", kernel_foo, 0);

But this doesn't seem to work.  When I try I do call my_meth{ "some_string" } I 
get `instance_eval': block not supplied (ArgumentError)

What am I doing wrong here?

Thanks,

Dan


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