image.rb

class Image
  def self.set_scope(description, criteria, params, attribute=:id_number)
    opts = criteria.options
    selector = criteria.selector
    scope_params = {}
    scope_params[:controller] = params[:controller]
    scope_params[:action] = params[:action]
    scope_params[:uploader_id] = params[:uploader_id]
    scope_params[:id] = params[:id]
    scope_params[:ignore_spoiler_for] = params[:ignore_spoiler_for]
    scope_params = scope_params.delete_if{|k,v|v == nil}

    key = "scope_#{description.downcase.gsub(" ","-").gsub(/[^a-z0-9\-]/,'')}_#{Digest::SHA1.hexdigest(description+opts.to_json+selector.to_json+scope_params.to_s+attribute.to_s)}"
    return Rails.cache.fetch(key, :expires_in=>21600, :race_condition_ttl=>360) { {scope_id: key, options: opts, selector: selector, description: description, params: scope_params, attribute: attribute} }
  end

  def self.get_scope(scope_id)
    d = Rails.cache.read(scope_id) rescue nil
    return d if d
    return {}
  end
end

images_controller.rb

class ImagesController < ApplicationController
  def index
    @hidden_tags = Tag.get_hidden_tags(current_user)
    @images = Image.order_by([:created_at, :desc]).not_in(tag_ids: @hidden_tags) # Make our criteria
    @list_scope = Image.set_scope("All Images", @images, params) # Store it in our scope
    @images = @images.page(params[:page]).per(current_user ? current_user.images_per_page : 15)
    respond_to do |format|
      format.html { render stream: true }
      format.json { render json: @images }
    end
  end
end