Rails - Jan 2009 - "obj.is_one_of? {Class1, Class2, ...}" as similar to "obj.is_a?(Class1) or obj.is_a?(Class2)"

I need to check if a given object is an instance of a range of
Classes, and I was wondering if I could do it by passing in is_a? an
hash of classes, instead of calling is_a? for each class I have to
compare...
As I state in the subject (obj.is_one_of? {Class1, Class2, ...}), this
could justify a method "obj.is_one_of?" which returns true if the
object "obj" is an instance of Class1 or Class2...
Is there something that I''m missing?
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On Jan 16, 2009, at 12:21 PM, jmfreitas wrote:
> I need to check if a given object is an instance of a range of
> Classes,
Are you sure?  It would be more idiomatic to check for duck-typing:
	obj.respond_to? :my_method
or to just call it and deal with the consequences:
	begin
	  obj.my_method
	rescue NoMethodError
	  # deal with it
	end

You already have something similar with:
	case obj
	when Class1, Class2
	  # Yippee!
	else
	  # Drat!
	end

> and I was wondering if I could do it by passing in is_a? an
> hash of classes, instead of calling is_a? for each class I have to
> compare...
> As I state in the subject (obj.is_one_of? {Class1, Class2, ...}), this
> could justify a method "obj.is_one_of?" which returns true if the
> object "obj" is an instance of Class1 or Class2...
> Is there something that I''m missing?
What are you trying to do that causes you to want this?

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org



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Thanks so much for the quick and useful reply...
The suggestion to use "case obj when Class1, Class2" completely
fulfills my needs, most appreciated :-D


On 16 Jan, 17:39, Rob Biedenharn
<R...-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org>
wrote:
> On Jan 16, 2009, at 12:21 PM, jmfreitas wrote:
>
> > I need to check if a given object is an instance of a range of
> > Classes,
>
> Are you sure?  It would be more idiomatic to check for duck-typing:
>         obj.respond_to? :my_method
> or to just call it and deal with the consequences:
>         begin
>           obj.my_method
>         rescue NoMethodError
>           # deal with it
>         end
>
> You already have something similar with:
>         case obj
>         when Class1, Class2
>           # Yippee!
>         else
>           # Drat!
>         end
>
> > and I was wondering if I could do it by passing in is_a? an
> > hash of classes, instead of calling is_a? for each class I have to
> > compare...
> > As I state in the subject (obj.is_one_of? {Class1, Class2, ...}), this
> > could justify a method "obj.is_one_of?" which returns true
if the
> > object "obj" is an instance of Class1 or Class2...
> > Is there something that I''m missing?
>
> What are you trying to do that causes you to want this?
>
> -Rob
>
> Rob Biedenharn          http://agileconsultingllc.com
> R...-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org
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