Why do I get "undefined method `start_with?'"?

Question

I get:

undefined method 'start_with?' for "-f":String (NoMethodError)

At this line:

if arg.start_with?("-v")

This worked on a different machine apparently so I'm assuming it could be a problem with my Ruby installation. Any ideas?

Answer 1

String#start_with? was introduced in Ruby 1.8.7. You're apparently using an earlier version, which is (sadly) not uncommon, but the 1.8 series is being retired shortly and you should considering upgrading.

I can't find any reference to String#start_with? in the 1.8.6 docs, but it exists in the 1.8.7 docs.