From: Park Heesob <phasis@...>
Date: 2003-11-28T22:11:45+09:00
Subject: Re: rb_hash_aref question: symbols vs strings

Hi,


>
> Hi all,
>
> I'm writing an extension, and I'm having a little trouble with using a
> hash for keyword arguments.  I want to allow a API like this:
>
> Foo.test(
>    :bar => "hello",
>    'baz' => "world"
> )
>
> In the extension to get the key value I do this:
>
> VALUE rbBar = rb_hash_aref(myHash,rb_str_new2("bar"));
>
> If the key "bar" is a string, that works fine.  However, that returns
> nil (not a symbol) if "bar" is a symbol.  I know I can do rb_iterate
> and I can detect if hash keys are symbols, but I don't know how to
> permanately change the key back to a string, i.e. it appears to pass a
> copy of the hash, rather than a reference.
>
> // Iterate over hash.  Assume that rb_sym2str() works properly.
> static VALUE parse_hash(VALUE array, VALUE class)
> {
>    VALUE key, tkey, val;
>
>    key = rb_ary_entry(array, 0); // Get key
>    val = rb_ary_entry(array, 1); // Get value
>
>    if(TYPE(key) == T_SYMBOL){
>       key = rb_sym2str(key); // Convert T_SYMBOL to T_STRING
>       printf("Key is now: %s\n",STR2CSTR(key)); // Verify string
>       rb_ary_store(array,0,key); // Doesn't work
>    }
>
>    return array;
> }
>
> Any ideas?
>
> Regards,
>
> Dan
>
>
Here is my solution:

hash = Foo.test(
   :bar => "hello",
   'baz' => "world"
)

static VALUE
test(VALUE klass,VALUE myHash)
{

    int i;
    VALUE ary = rb_funcall(myHash,rb_intern("keys"),0);

    for(i=0;i<RARRAY(ary)->len;i++)
    {
        if(TYPE(RARRAY(ary)->ptr[i])==T_STRING)
            printf("key = %s, val = %s\n",
                STR2CSTR(RARRAY(ary)->ptr[i]),
                STR2CSTR(rb_hash_aref(myHash,RARRAY(ary)->ptr[i])));
        if(TYPE(RARRAY(ary)->ptr[i])==T_SYMBOL)
            printf("key = %s, val = %s\n",

STR2CSTR(rb_funcall(RARRAY(ary)->ptr[i],rb_intern("inspect"),0)),
                STR2CSTR(rb_hash_aref(myHash,RARRAY(ary)->ptr[i])));
    }

    rb_hash_aset(myHash, rb_str_new2("baz"), rb_str_new2("aaa"));
    rb_hash_aset(myHash, rb_eval_string(":bar"), rb_str_new2("bbb"));

    for(i=0;i<RARRAY(ary)->len;i++)
    {
        if(TYPE(RARRAY(ary)->ptr[i])==T_STRING)
            printf("key = %s, val = %s\n",
                STR2CSTR(RARRAY(ary)->ptr[i]),
                STR2CSTR(rb_hash_aref(myHash,RARRAY(ary)->ptr[i])));
        if(TYPE(RARRAY(ary)->ptr[i])==T_SYMBOL)
            printf("key = %s, val = %s\n",

STR2CSTR(rb_funcall(RARRAY(ary)->ptr[i],rb_intern("inspect"),0)),
                STR2CSTR(rb_hash_aref(myHash,RARRAY(ary)->ptr[i])));
    }

    return myHash;
}

Regards,

Park Heesob