From: Admin Tensor <admin@...>
Date: 2011-12-02T23:17:03+09:00
Subject: Re: Native extension: arguments as a hash

Darryl Pierce wrote in post #1034735:
> I'm working on a native extension in C for Ruby 1.8.7. The method I'm
> working on must have the signature:
>
> def receive(receiver, opts = {})
>
> so that users can call:
>
> receiver(receiver, :timeout => 15) # :timeout is optional
>
> But I can't find a decent example of what such a method would look like
> in C. I've tried the following:
>
> static VALUE qpid_receiver(VALUE self, VALUE* varg)
> {
> }

Hi,

I am using 1.9.2, but hopefully it doesn't change much.  To have command
with default values you can declare your function as

rb_define_method(yourCclass, "receive", (VALUE(*)(...))qpid_receiver, 
-1);

(Notice the -1; it means it's variable arguments).  Then you can define
your function as

static VALUE qpid_receiver(int argc, VALUE* argv, VALUE self)
{
  VALUE rcvr, opts;
  rb_scan_args(argc, argv, "11", &rcvr, &opts); // one has to be given,
                                                // one optional
  if (NIL_P(opts))         // if opts is not given
    opts = rb_hash_new();  // make it a hash; maybe in 1.8.7 new hash is
                           // created differently

  // Continued with the rest...
}

I haven't compile the code, so maybe there are some typos.  Also, beside
-1, you can also have -2 for variable arguments, but the syntax is
rather different.  Hope this helps.

Regards,

Bill

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