I'd rather have this check if it's a String, instead of if it responds to :to_str; the contract (if there even is such a thing) on what to_s means vs to_str is not really clear in the docs and certainly not clear to me as a reader :P

I'll change this post-merge.

Sure, I actually wasn't sure if I should check for the type or the method. :)

I don't think there's any strict rule to play here, Ruby's a very flexible language in this respect. My personal habit is to either check for type or check for a method. Oddly, I've never seen this 'to_ary' and 'to_str' methods used in 7 years of ruby programming. Weird! :P

For my own learning -

Poking around String#to_str has really poor docs "returns the receiver" as does Array#to_ary which says "returns self".

Wondering what else has to_ary I asked for Enumerator#to_ary docs, and this method doesn't exist. Range#to_ary also does not exist.

Based on this, I think to_str and to_ary are weird, unclear, and we should not use them.

I'll merge as-is and switch to using type checks.

I do believe that in most cases multiple ways of getting the object type will work.
As for this...response_to? makes it (imho) more duck-type-like than just checking the type of object.
You dont really get advantages from respond_to? in this case.
Nevertheless to_str and to_ary are no methods, they are symbols for the respond_to? method.