Assigning cases to users. A de-factoring of https://gist.github.com/dhh/9348053

case_assignments_controller.rb

class Case::AssignmentsController < ApplicationController
  before_action :set_case, :set_new_owner
  
  def create
    ActiveRecord::Base.transaction do
      # update case owner
      @case.update! case_params.merge(owner: @new_owner)
  
      # transfer open tasks to new owner
      @case.tasks.open.each { |task| task.update!(owner: @new_owner) }
      
      # create `initial` task
      if create_initial_contact_task?
        @case.tasks.create!(kind: :initial, comments: comments)
      end
  
      # record the event
      @case.events.create! activity_params.merge(activity: :assigned, creator: @current_user)
    end
  end
  
  private
  
  def set_case
    @case = @current_account.cases.find(params[:case][:id])
  end
  
  def set_new_owner
    @new_owner = @current_account.users.find(params[:case][:owner_id])
  end
  
  def create_initial_contact_task?
    !!params.require(:case).permit(:require_initial) && @new_owner.tasks.initials?
  end
  
  def case_params
    params.require(:case).permit(:distribute_at, :distribute_rule_name)
  end

  def activity_params
    params.require(:case).permit(:comments)
  end
end

event.rb

class Event < ActiveRecord::Base
  belongs_to :eventable, polymorphic: true
  
  store_accessor :details, :activity, :creator, :comments
end

task.rb

class Task < ActiveRecord::Base
  belongs_to :user
  belongs_to :case
  
  enum status: [:open, :closed]
  
  has_many :events, as: :eventable
end

user.rb

class User
  has_many :tasks do
    def initials?
      where(kind: :initial).exist?
    end
  end
end