Re: singleton methods vs. meta instance methods

Hi --

On Sun, 14 Dec 2008, Brian Candler wrote:

> Daniel DeLorme wrote:
>> Furthermore this does not happen with builtin classes.
>
> I'm not sure what you mean by that part. I get the same if I use String
> instead of your class A:
>
> a = String
> a_meta = (class << a;self;end)
> def a.foobar; end
> p a.singleton_methods
> p a_meta.instance_methods(false)
>
> with 1.8.6p114 I get:
> ["foobar"]
> ["allocate", "foobar", "superclass", "new"]
>
> with 1.9.1-preview2 I get:
> [:try_convert, :foobar]
> [:try_convert, :foobar, :allocate, :new, :superclass]
>
> But notice what happens if I try an *instance* of String (which is
> comparable to what you were doing with an *instance* of class Object)
>
> a = String.new
> a_meta = (class << a;self;end)
> def a.foobar; end
> p a.singleton_methods(false)
> p a_meta.instance_methods(false)
>
> ["foobar"]
> ["split", "rstrip!", "to_sym", "swapcase", "chop", "foobar", "empty?",
> "swapcase!", "to_f", "casecmp", "rindex", "intern", "tr", "to_s",
> "reverse!", "strip!", "match", "hex", "each", "include?", "slice",
> "next!", "*", "downcase!", "downcase", "sub", "+", "=~", "upto",
> "concat", "lstrip", "each_byte", "succ!", "chop!", "size", "dump",
> "rjust", "squeeze", "delete!", "eql?", "next", "reverse", "sub!",
> "insert", "chomp", "[]", "inspect", "tr!", "replace", "[]=", "scan",
> "tr_s", "lstrip!", "succ", "<<", "oct", "gsub", "capitalize!", "to_i",
> "hash", "capitalize", "crypt", "index", "chomp!", "rstrip", "sum",
> "upcase!", "center", "upcase", "count", "squeeze!", "unpack", "<=>",
> "strip", "==", "length", "gsub!", "each_line", "slice!", "ljust",
> "to_str", "%", "delete", "tr_s!"]
>
> So you can see the instance methods of the object's metaclass include
> the instance methods of that object's class. From one point of view this
> seems reasonable to me; the metaclass is like a 'private subclass' to
> the real class.
>
>> From another point of view, you might expect instance_methods(false) not
> to return those methods. But I think that just explains why we have a
> separate singleton_methods method - if you *really* want just the
> singleton methods, not including the methods of the concrete class, call
> that.

I've never liked the "false" flag thing, since it's obscure to begin
with. If it doesn't actually mean "defined in exactly this class",
then I'm not sure what purpose it serves at all.

(Don't mean to sound curmudgeonly -- am multi-tasking, which almost
always means I shouldn't post to ruby-talk since whatever the main
point is is probably zooming past me :-)


David

-- 
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