From: Albert Schlef <albertschlef@...>
Date: 2008-05-07T10:51:37+09:00
Subject: Re: Yet another question about extending ruby with C

Bryan Richardson wrote:
> Say I have the following:
>
> typedef struct {
>   char* name;
> } Foo;
>
> [...]
>
> static VALUE foo_init(VALUE self) {
>   VALUE str;
>   char* name = "Bryan";
>   str = rb_str_new2(name);
>   rb_iv_set(self, "@name", str);
>   return self;
> }
>
> static VALUE test(VALUE self, VALUE arg) {
>   Foo* f;
>   Data_Get_Struct(arg, Foo, f);
>   printf("Name: %s\n", f->name);
>   return Qnil;
> }
> 
> [...]
> 
> If I do the following, everything works perfectly and I see my name
> printed
> on the screen:
> 
> [...]
> b.test(f)  // prints "Bryan"

"works perfectly"? I don't see how it can print "Bryan", for two 
reasons:

1. It's supposed to print "Name: Bryan", not "Bryan".

2. But it can't print "Name: Bryan" either. That's because in foo_init() 
you aren't settings f->name to "Bryan". Instead, you're settings an 
instance variable, "@name", to "Bryan". It happens that "@name" has a 
similar name to char *name, but these two variables aren't related at 
all.

Last but not least:

If you want ppl to help you, you must make it easier for them to help 
you. Do that by choosing _sane_ names for your 
methods/structures/variables. I had a hard time following your code (and 
that in your previous question). 'test', 'Test' and 'Foo' aren't 
meaningful names. Change them to make_person, Person, and person_rec.
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