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

Rails
1

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?

2

Thanks so much for the quick and useful reply…
The suggestion to use “case obj when Class1, Class2” completely
fulfills my needs, most appreciated :smiley:

3

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 B. http://agileconsultingllc.com
[email protected]