How to reject a post based on some attributes

reject_post.rb

# We are using the default ruby http client for the request to the
# shortened url, because otherwise a Gemfile or something different
# would be necessary

require 'net/http'

# I am using an example url from webdesignshare.com (with url shortener)
uri = URI('http://url.tusiad.org/make-people-stay-website')
res = Net::HTTP.get_response(uri)

# Here you could also countercheck a blacklist array or something
# Just check for the domain name, because otherwise wds will change to https
if res.code === '301' && res.read_header['Location'].include?('webdesignshare.com') {
  # Reject or do something different
  @post.reject!
} else {
  # Accept the posting here posting
  @post.accept!
}