Question

Im new to Ruby and Rails so forgive me if this an easy question. Im trying to check when a user passes in an IMG url in my form, that it is a valid url. Here is my code:

if params[:url].include? 'http://' && (params[:url].include? '.jpg' || params[:url].include? '.png')

This returns and error. Is this is even the best way to go about it? What should I do differently? Thanks.

Answer 1

if my_str =~ %r{\Ahttps?://.+\.(?:jpe?g|png)\z}i

Regex explained:

• %r{...} — regex literal similar to /.../, but allows / to be used inside without escaping
• \A — the start of the string (^ is just the start of the line)
• http — the literal text
• s? — optionally followed by an “s” (to allow https://)
• :// — the literal text (to prevent something like http-whee.jpg)
• .+ — one or more characters (that aren’t a newline)
• \. — a literal period (make sure this is an extension we’re looking at)
• (?:aaa|bbb) — allow either aaa or bbb here, but don’t capture the result
• jpe?g — either “jpg” or “jpeg”
• png — the literal text
• \z — the end of the string ($ is just the end of the line)
• i — make the match case-insensitive (allow for .JPG as well as .jpg)

However, you might be able to get away with just this (more readable) version:

allowed_extensions = %w[.jpg .jpeg .png]
if my_str.start_with?('http://') &&
   allowed_extensions.any?{ |ext| my_str.end_with?(ext) }