Ruby中的两个比较，除非

Question

Im ruby beginner and very frustrated with this code:

unless ((f[-4..-5] == '.png') || (f[-4..-5] == '.jpg'))

Somehow the second comparison is not recognized by ruby! Whats wrong?

Answer 1

I think you should use f[-4..-1] instead of f[-4..-5] .

Or you can use regular expression:

unless f =~ /\.(png|jpg)$/

or use String#end_with? :

unless f.end_with?('.png', '.jpg')

Answer 2

f[-4..-5] would be an empty string, which will never match '.png' . So the second term of your disjunction will never be evaluated.

If you are conditioning by the file extension, then you may do this:

case File.extname(f)
when ".png", ".jpg"
else
  ...
end

Answer 3

How is below :

ext_nm = File.extname(f)
unless [".png", ".jpg"].include? ext_nm