The Ruby %r{ } expression

Question

In a model there is a field

validates :image_file_name, :format => { :with => %r{\\.(gif|jpg|jpeg|png)$}i

It looks pretty odd for me.

Answer 1

\. => contains a dot
(gif|jpg|jpeg|png) => then, either one of these extensions
$ => the end, nothing after it
i => case insensitive

And it's the same as writing /\.(gif|jpg|jpeg|png)$/i.