How to implement revision control in rails app using paperclip and vestal versions - Tutorial link:- http://josephndungu.com/tutorials/revision-control-with-paperclip-rails

_form.html.erb

<%= form_for(@logo, :html => { :multipart => true })  do |f| %>
  <% if @logo.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@logo.errors.count, "error") %> prohibited this logo from being saved:</h2>

      <ul>
      <% @logo.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %><br>
    <%= f.text_field :name %>
  </div>

  <div class="field">
    <%= f.file_field :image %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

adding_paperclip_and_vs.rb

class Logo < ActiveRecord::Base
	versioned

	has_attached_file :image, 
			  :styles => { :medium => "400x400#" }
			  
	validates_attachment_content_type :image, :content_type => /\Aimage\/.*\Z/
end

Gemfile

# add paperclip
gem 'paperclip', '~>3.4.2'

# add vestal versions
gem 'vestal_versions', :git => 'git://github.com/laserlemon/vestal_versions'

latest.html.erb

<p id="notice"><%= notice %></p>

<p>
	<%= image_tag @logo.image.url(:medium) %>
</p>

<p>
  <strong>Name:</strong>
  <%= @logo.name %>
</p>

<p>
	<% if @logo.version > 1 %>
  	 	<%= link_to "Previous version", :version => @logo.version-1 %>
  	<% end %>

  	<% if params[:version] %>
  		<%= link_to "Latest version", :version => nil %>
	<% end %>
</p>

<%= link_to 'Edit', edit_logo_path(@logo) %> |
<%= link_to 'Back', logos_path %> |
Version <%= @logo.version %>

logo.rb

class Logo < ActiveRecord::Base
	versioned

	has_attached_file :image,  
			:keep_old_files => true,
			:styles => { :medium => "400x400#" },
			:url => "/assets/logos/:id/versions/:version/:style/:basename.:extension",
    			:path => ":rails_root/public/assets/logos/:id/versions/:version/:style/:basename.:extension"

    	validates_attachment_content_type :image, :content_type => /\Aimage\/.*\Z/

    	# keep versions
    	
  	Paperclip.interpolates :version do |attachment, style|
    		attachment.instance.version.to_s
  	end
end

logo_version.html.erb

<p id="notice"><%= notice %></p>

<p>
	<%= image_tag @logo.image.url(:medium) %>
</p>

<p>
  <strong>Name:</strong>
  <%= @logo.name %>
</p>


<%= link_to 'Edit', edit_logo_path(@logo) %> |
<%= link_to 'Back', logos_path %> |
Version <%= @logo.version %>

prev_and_latest.html.erb

<p id="notice"><%= notice %></p>

<p>
	<%= image_tag @logo.image.url(:medium) %>
</p>

<p>
  <strong>Name:</strong>
  <%= @logo.name %>
</p>

<p>
	<% if @logo.version > 1 %>
  	 	<%= link_to "Previous version", :version => @logo.version-1 %>
  	<% end %>

  	<% if params[:version] %>
  		<%= link_to "Latest version", :version => nil %>
	<% end %>
</p>

<%= link_to 'Edit', edit_logo_path(@logo) %> |
<%= link_to 'Back', logos_path %> |
Version <%= @logo.version %>

previous.html.erb

<p id="notice"><%= notice %></p>

<p>
	<%= image_tag @logo.image.url(:medium) %>
</p>

<p>
  <strong>Name:</strong>
  <%= @logo.name %>
</p>

<p>
	<% if @logo.version > 1 %>
  	 	<%= link_to "Previous version", :version => @logo.version-1 %>
  	<% end %>
</p>

<%= link_to 'Edit', edit_logo_path(@logo) %> |
<%= link_to 'Back', logos_path %> |
Version <%= @logo.version %>

show_action.rb

class LogosController < ApplicationController
  before_action :set_logo, only: [:show, :edit, :update, :destroy]

  # more actions

  # GET /logos/1
  # GET /logos/1.json
  def show
    @logo.revert_to(params[:version].to_i) if params[:version]
  end

  # GET /logos/new
  def new
    @logo = Logo.new
  end

  # more code follows
end

update_logo_params.rb

class LogosController < ApplicationController
  before_action :set_logo, only: [:show, :edit, :update, :destroy]

  # more code here

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_logo
      @logo = Logo.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def logo_params
      params.require(:logo).permit(:name, :image)
    end
end

versioning_with_paperclip.rb

# config/initializers/versioning_with_paperclip.rb

module Paperclip
  class Attachment
    def save
      flush_deletes unless @options[:keep_old_files]
      flush_writes
      @dirty = false
      true
    end
  end
end