Question

I have two models that I currently have as STI.

class Event
class BlockedTime < Event
class Appointment < Event

The models are similar except that ‘Appointment’ has_one ‘client’ and has_one ‘service’, whereas ‘BlockedTime’ has neither of those associations.

Additionally, I want to be able to convert between the two types easily, and when I search, I’m usually searching on both types together, not one or the other. For those reasons I hesitate to make them separate tables.

For switching between the types, I currently do this in the same form, using the parent ‘Event’ type, and storing the ‘type’ as a hidden field, but this is definitely not working out well. I have to do all sorts of conversions in the controller to check validations, etc.

How would you recommend modeling this?

Answer 1

So, if I were having this problem I would probably model the database differently.

Instead of a STI/Inheritance pattern, I would use a Composition pattern. So:

class Appointment
  belongs_to :block_time, :class_name => "BlockTime"
  ...
end

class BlockTime
   has_one :appointment
   accepts_nested_attributes_for :appointment, :allow_destroy => :true, 
                                               :reject_if => :all_blank

  ...
end

Controller

class AppointmentsController < ApplicationController
  ...

  def new
    @block_time = BlockTime.new
    @block_time.appointment or @block_time.build_appointment
    ...
  end

  def edit
    @block_time = BlockTime.includes(:appointment).find(params[:id])
    @block_time.appointment or @block_time.build_appointment
  end

  ...
end

Form or at least part of the form

<%= f.fields_for :appointment do |g| %>
  <div>
    <%= g.radio_button :_destroy, "1", :checked => !g.object.persisted? %>
    <%= g.label :_destroy_1, "Has no Appointment" %>

    <%= g.radio_button :_destroy, "0", :checked => g.object.persisted? %>
    <%= g.label :_destroy_0, "Has Appointment" %>
  </div>

  <p>
    Client: <%= g.text_field :client %>
  </p>
<% end %>

This part of the form uses persisted? to check to see if the Appointment object is a new record or has been persisted to the database. Then if it has been and you want to remove it then it will throw the _destroy flag for accepts_nested_attributes_for and delete the existing appointment association to make it a free BlockTime.

Then you could include all the Appointment fields in this form too. You might want to cook up some javascript to disable/enable fields depending on the radio_button selection