How do I implement hashids in ruby on rails

I will go ahead and apologize upfront as I am new to ruby and rails and I cannot for the life of me figure out how to implement using hashids in my project. The project is a simple image host. I have it already working using Base58 to encode the sql ID and then decode it in the controller. However I wanted to make the URLs more random hence switching to hashids.

I have placed the hashids.rb file in my lib directory from here: https://github.com/peterhellberg/hashids.rb

Now some of the confusion starts here. Do I need to initialize hashids on every page that uses hashids.encode and hashids.decode via

hashids = Hashids.new("mysalt")

I found this post (http://zogovic.com/post/75234760043/youtube-like-ids-for-your-activerecord-models) which leads me to believe I can put it into an initializer however after doing that I am still getting NameError (undefined local variable or method `hashids' for ImageManager:Class)

so in my ImageManager.rb class I have

require 'hashids'

class ImageManager
class << self
def save_image(imgpath, name)

  mime = %x(/usr/bin/exiftool -MIMEType #{imgpath})[34..-1].rstrip
  if mime.nil? || !VALID_MIME.include?(mime)
    return { status: 'failure', message: "#{name} uses an invalid format." }
  end

  hash = Digest::MD5.file(imgpath).hexdigest
  image = Image.find_by_imghash(hash)

  if image.nil?
    image = Image.new
    image.mimetype = mime
    image.imghash = hash
    unless image.save!
      return { status: 'failure', message: "Failed to save #{name}." }
    end

    unless File.directory?(Rails.root.join('uploads'))
      Dir.mkdir(Rails.root.join('uploads'))
    end
    #File.open(Rails.root.join('uploads', "#{Base58.encode(image.id)}.png"), 'wb') { |f| f.write(File.open(imgpath, 'rb').read) }
    File.open(Rails.root.join('uploads', "#{hashids.encode(image.id)}.png"), 'wb') { |f| f.write(File.open(imgpath, 'rb').read) }
  end

  link = ImageLink.new
  link.image = image
  link.save

#return { status: 'success', message: Base58.encode(link.id) }
return { status: 'success', message: hashids.encode(link.id) }
end

private

    VALID_MIME = %w(image/png image/jpeg image/gif)
  end
end

And in my controller I have:

require 'hashids'

class MainController < ApplicationController
MAX_FILE_SIZE = 10 * 1024 * 1024
MAX_CACHE_SIZE = 128 * 1024 * 1024

@links = Hash.new
@files = Hash.new
@tstamps = Hash.new
@sizes = Hash.new
@cache_size = 0

class << self
  attr_accessor :links
  attr_accessor :files
  attr_accessor :tstamps
  attr_accessor :sizes
  attr_accessor :cache_size
  attr_accessor :hashids
end

def index
end

def transparency
end

def image
  #@imglist = params[:id].split(',').map{ |id| ImageLink.find(Base58.decode(id)) }
  @imglist = params[:id].split(',').map{ |id| ImageLink.find(hashids.decode(id)) }
end

def image_direct
  #linkid = Base58.decode(params[:id])
  linkid = hashids.decode(params[:id])

  file =
    if Rails.env.production?
      puts "#{Base58.encode(ImageLink.find(linkid).image.id)}.png"
      File.open(Rails.root.join('uploads', "#{Base58.encode(ImageLink.find(linkid).image.id)}.png"), 'rb') { |f| f.read }
    else
      puts "#{hashids.encode(ImageLink.find(linkid).image.id)}.png"
      File.open(Rails.root.join('uploads', "#{hashids.encode(ImageLink.find(linkid).image.id)}.png"), 'rb') { |f| f.read }
    end

  send_data(file, type: ImageLink.find(linkid).image.mimetype, disposition: 'inline')
end

def upload
  imgparam = params[:image]

  if imgparam.is_a?(String)
    name = File.basename(imgparam)
    imgpath = save_to_tempfile(imgparam).path
  else
    name = imgparam.original_filename
    imgpath = imgparam.tempfile.path
  end

  File.chmod(0666, imgpath)
  %x(/usr/bin/exiftool -all= -overwrite_original #{imgpath})
  logger.debug %x(which exiftool)
  render json: ImageManager.save_image(imgpath, name)
end

private

  def save_to_tempfile(url)
  uri = URI.parse(url)

  http = Net::HTTP.new(uri.host, uri.port)
  http.use_ssl = uri.scheme == 'https'
  http.start do
    resp = http.get(uri.path)
    file = Tempfile.new('urlupload', Dir.tmpdir, :encoding => 'ascii-8bit')
    file.write(resp.body)
    file.flush
    return file
  end
end
end

Then in my image.html.erb view I have this:

<%
   @imglist.each_with_index { |link, i|
   id = hashids.encode(link.id)
   ext = link.image.mimetype.split('/')[1]
   if ext == 'jpeg'
     ext = 'jpg'
   end
   puts id + '.' + ext
%>

Now if I add

hashids = Hashids.new("mysalt")

in ImageManager.rb main_controller.rb and in my image.html.erb I am getting this error:

ActionView::Template::Error (undefined method `id' for #<Array:0x000000062f69c0>)

So all in all implementing hashids.encode/decode is not as easy as implementing Base58.encode/decode and I am confused on how to get it working... Any help would be greatly appreciated.

Solution

I would suggest loading it as a gem by including it into your Gemfile and running bundle install. It will save you the hassle of requiring it in every file and allow you to manage updates using Bundler.

Yes, you do need to initialize it wherever it is going to be used with the same salt. Would suggest that you define the salt as a constant, perhaps in application.rb.

The link you provided injects hashids into ActiveRecord, which means it will not work anywhere else. I would not recommend the same approach as it will require a high level of familiarity with Rails.

You might want to spend some time understanding ActiveRecord and ActiveModel. Will save you a lot of reinventing the wheel. :)