How do I implement hashids in ruby on rails - ruby

Question

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.

Answer 1

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. :)

Answer 2

Before everythink you should just to test if Hashlib is included in your project, you can run command rails c in your project folder and make just a small test :
>> my_id = ImageLink.last.id
>> puts Hashids.new(my_id)
If not working, add the gem in gemfile (that anyway make a lot more sence).
Then, I think you should add a getter for your hash_id in your ImageLink model.
Even you don't want to save your hash in the database, this hash have it's pllace in your model. See virtual property for more info.
Remember "Skinny Controller, Fat Model".
class ImageLink < ActiveRecord::Base
def hash_id()
# cache the hash
#hash_id ||= Hashids.new(id)
end
def extension()
# you could add the logic of extension here also.
ext = image.mimetype.split('/')[1]
if ext == 'jpeg'
'jpg'
else
ext
end
end
end
Change the return in your ImageManager#save_image
link = ImageLink.new
link.image = image
# Be sure your image have been saved (validation errors, etc.)
if link.save
{ status: 'success', message: link.hash_id }
else
{status: 'failure', message: link.errors.join(", ")}
end
In your template
<%
#imglist.each_with_index do |link, i|
puts link.hash_id + '.' + link.extension
end # <- I prefer the do..end to not forgot the ending parenthesis
%>
All this code is not tested...

Answer 3

I was looking for something similar where I can disguise the ids of my records. I came across act_as_hashids.
https://github.com/dtaniwaki/acts_as_hashids
This little gem integrates seamlessly. You can still find your records through the ids. Or with the hash. On nested records you can use the method with_hashids.
To get the hash you use to_param on the object itself which result in a string similar to this ePQgabdg.
Since I just implemented this I can't tell how useful this gem will be. So far I just had to adjust my code a little bit.
I also gave the records a virtual attribute hashid so I can access it easily.
attr_accessor :hashid
after_find :set_hashid
private
def set_hashid
self.hashid = self.to_param
end