From: Daniel Berger <djberg96@...>
Date: 2002-04-19T12:08:07+09:00
Subject: Re: Confused by example in Pickaxe book


"Christian Boos" <cboos@bct-technology.com> wrote in message
news:CHEMJHJAJKOIPELDPKKBCELGCAAA.cboos@bct-technology.com...
> Hello,
>
> You should have a look to the signature of those
> methods. It's pretty simple:
>
> > -----Original Message-----
> > From: Daniel Berger [mailto:djberg96@hotmail.com]
> > Sent: Thursday, April 18, 2002 5:47 PM
> > To: ruby-talk ML
> > Subject: Confused by example in Pickaxe book
> >
> >
> > Hi all,
> >
> > On p. 181 of the Pickaxe, the example defines the "initialize" method
> > like this:
> >
> > rb_define_method(cCDPlayer,"initialize",cd_init,1);
> >
>
> .. CDPlayer#initialize will take one fixed argument.
>
> > Yet, in the "new" method it's called like this:
> >
> > rb_obj_call_init(tdata,1,argv);
> >
>
> This function uses a argc-argv style list of VALUEs.
> '1' is the count of elements in the C array of VALUEs.
> Internally, 'rb_obj_call_init' will use 'rb_funcall2' to call
> the "initialize" method on the 'tdata' object.
>
> > First, isn't that 2 arguments instead of 1 (remembering to exclude
> > 'self', i.e. tdata, as an argument).  What is the '1' for?
> >
> > Second, what is the purpose of this?
> >
> > VALUE argv[1];
> > argv[0] = unit;
> >
> > What is happening here?
> >
>
> .. when using 'rb_obj_call_init', one has to pack
> the arguments in a C array of VALUEs, even if there's
> only one argument.
> I guess that in that specific case, one could write the call
> in a shorter way:
>
>  rb_obj_call_init(tdata,1,&unit);
>
> .. but this would be even more confusing :)
>
> > Much confused.
> >
>
> Hope it helps :)

Thanks go to both you and Guy.  I'm less confused now. :)

Dan