form_object.rb

class UsersController < ApplicationController
  def index
    user_search = UserSearch.new(params[:user_search])
    @users = User.by_user_search(user_search)
  end
end
 
# user search form object
class UserSearch
  include Virtus.model

  attribute :name, String
  attribute :rating, Integer, default: 4 # setting default values
  attribute :skills, ArrayFromCommaSeparatedString # parsing parameters
end

class User < ActiveRecord::Base
   scope :by_user_search, ->(user_search) {
    scopes = []
    scopes << where('name like ?', "%#{user_search.name}%") if user_search.name
    scopes << where('rating > ?', rating)
    scopes << tagged_with(user_search.skills, any: true) if user_search.skills
    scopes.inject(User.all) { |r,e| r.merge(e) }
  }
end