Let’s imagine we want to regexp a string and print the capitalized match out. We start with one of the followings:
str.match(/(regexp)/)[1].capitalize
/(regexp)/.match(str)[1].capitalize
This works fine on matched strings. Being called on the input with no matches it indeed results in annoying:
# ⇒ NoMethodError: undefined method `[]' for nil:NilClass
So we come to spaghetti if-then checks like:
m = str.match(/(regexp)/)
m1 = m[1] if m
cap = m1.cap if m1
We got bogged down in checking while the only goal was to write a oneliner to
either capitalize match or gracefully keep silent. Happily, ruby has a not
wide well-known way to perform exactly the task we wanted. It’s the
String#[regexp, fixnum] method:
(str.match[/(regexp)/, 1] || '').capitalize