End and NoMethodError

require 'rubygems'
require 'open-uri'
require 'nokogiri'

class ImageDownLoad
    def self.checkLink(strLink)
        if (strLink.include?('imgur.com'))
            downloadImgur(strLink)
        else if (strLink.include?('4chan.org'))
            downloadChan(strLink)
        else
            puts "Enter a 4chan or Imgur link"
        end
    end
    def self.downloadImgur(strLink)

    end
    def self.downloadChan(strLink)
        page = Nokogiri::HTML(open(strLink))
        img = page.xpath(%Q[//*[@id="f637181555"]/a/@href])
        img.map { |image|  File.write(rand.to_s + '.jpg', open(image).read, {mode: 'wb'})}
    end
end

client = ImageDownLoad.new
while (true) do
    puts "Enter URL to rip: "
    strLink = gets.chomp
    if (strLink.include?('break'))
        break
    end
    client.checkLink(strLink)
end