Replace Subclasses with Strategies: Step Thirteen

* Always instantiate the same root class

example_app/app/controllers/questions_controller.rb

@@ -31,13 +31,13 @@ def update
   private
 
   def build_question
-    @question = type.constantize.new(question_params)
+    @question = Question.new(question_params)
     @question.build_submittable(type, submittable_params)
     @question.survey = @survey
   end
 
   def type
-    params[:question][:type]
+    params[:question][:submittable_type]
   end
 
   def question_params

example_app/app/controllers/types_controller.rb

@@ -2,7 +2,7 @@ class TypesController < ApplicationController
   def new
     @question = Question.find(params[:question_id])
     assign_type
-    @new_question = type.constantize.new
+    @new_question = Question.new
     @new_question.build_submittable(type, {})
   end
 
@@ -37,6 +37,6 @@ def submittable_attributes
   end
 
   def type
-    params[:question][:type]
+    params[:question][:submittable_type]
   end
 end

example_app/app/models/question.rb

@@ -1,10 +1,14 @@
 class Question < ActiveRecord::Base
   include ActiveModel::ForbiddenAttributesProtection
 
-  QUESTION_TYPES = %w(OpenQuestion MultipleChoiceQuestion ScaleQuestion).freeze
+  QUESTION_TYPES = %w(
+    OpenSubmittable
+    MultipleChoiceSubmittable
+    ScaleSubmittable
+  ).freeze
 
   validates :submittable, associated: true
-  validates :type, presence: true, inclusion: QUESTION_TYPES
+  validates :submittable_type, presence: true, inclusion: QUESTION_TYPES
   validates :title, presence: true
 
   belongs_to :submittable, polymorphic: true
@@ -33,7 +37,7 @@ def summarize(summarizer)
   def switch_to(type, new_attributes, submittable_attributes)
     attributes = self.attributes.merge(new_attributes)
     cloned_attributes = attributes.except('id', 'type', 'submittable_type')
-    new_question = type.constantize.new(cloned_attributes)
+    new_question = Question.new(cloned_attributes)
     new_question.build_submittable(type, submittable_attributes)
     new_question.id = id
 

example_app/app/views/multiple_choice_questions/_multiple_choice_question.html.erb → example_app/app/views/multiple_choice_submittables/_multiple_choice_submittable.html.erb

@@ -1,5 +1,5 @@
 <ol>
-  <% submittable.options.each do |option| -%>
+  <% multiple_choice_submittable.options.each do |option| -%>
     <li>
       <%= submission_fields.radio_button :text, option.text, id: dom_id(option) %>
       <%= content_tag :label, option.text, for: dom_id(option) %>

example_app/app/views/questions/_form.html.erb

@@ -1,8 +1,8 @@
 <%= simple_form_for question, as: :question, url: url do |form| -%>
-  <%= form.hidden_field :type %>
+  <%= form.hidden_field :submittable_type %>
   <%= form.input :title %>
   <%= render(
-    "#{question.to_partial_path}_form",
+    "#{question.submittable.to_partial_path}_form",
     submittable: question.submittable,
     form: form
   ) %>

example_app/app/views/questions/edit.html.erb

@@ -5,20 +5,26 @@
 
   <%= link_to(
     'Scale Question',
-    new_question_type_path(@question, question: { type: 'ScaleQuestion' })
+    new_question_type_path(
+      @question,
+      question: { submittable_type: 'ScaleSubmittable' }
+    )
   ) %>
 
   <%= link_to(
     'Multiple Choice Question',
     new_question_type_path(
       @question,
-      question: { type: 'MultipleChoiceQuestion' }
+      question: { submittable_type: 'MultipleChoiceSubmittable' }
     )
   ) %>
 
   <%= link_to(
     'Open Question',
-    new_question_type_path(@question, question: { type: 'OpenQuestion' })
+    new_question_type_path(
+      @question,
+      question: { submittable_type: 'OpenSubmittable' }
+    )
   ) %>
 </p>
 

example_app/app/views/scale_questions/_scale_question.html.erb → example_app/app/views/scale_submittables/_scale_submittable.html.erb

@@ -1,5 +1,5 @@
 <ol>
-  <% submittable.steps.each do |step| -%>
+  <% scale_submittable.steps.each do |step| -%>
     <li>
       <%= submission_fields.radio_button :text, step %>
       <%= submission_fields.label "text_#{step}", label: step %>

example_app/app/views/surveys/show.html.erb

@@ -6,17 +6,26 @@
 
 <%= link_to(
   'Add Multiple Choice Question',
-  new_survey_question_path(@survey, question: { type: 'MultipleChoiceQuestion' })
+  new_survey_question_path(
+    @survey,
+    question: { submittable_type: 'MultipleChoiceSubmittable' }
+  )
 ) %>
 
 <%= link_to(
   'Add Open Question',
-  new_survey_question_path(@survey, question: { type: 'OpenQuestion' })
+  new_survey_question_path(
+    @survey,
+    question: { submittable_type: 'OpenSubmittable' }
+  )
 ) %>
 
 <%= link_to(
   'Add Scale Question',
-  new_survey_question_path(@survey, question: { type: 'ScaleQuestion' })
+  new_survey_question_path(
+    @survey,
+    question: { submittable_type: 'ScaleSubmittable' }
+  )
 ) %>
 
 <%= simple_form_for [@survey, @completion] do |form| -%>
@@ -26,9 +35,8 @@
         <%= form.fields_for "answers_attributes[#{question.id}]", Answer.new do |submission_fields| -%>
           <%= submission_fields.label :text, label: question.title %>
           <%= render(
-            question,
-            submission_fields: submission_fields,
-            submittable: question.submittable
+            question.submittable,
+            submission_fields: submission_fields
           ) %>
           <%= link_to 'Edit', edit_question_path(question) %>
         <% end -%>

example_app/app/views/types/new.html.erb

@@ -4,7 +4,7 @@
   url: question_types_path(@question)
 ) do |form| -%>
 
-  <%= form.hidden_field :type %>
+  <%= form.hidden_field :submittable_type %>
   <%= render(
     "#{@new_type}s/#{@new_type}_form",
     question: @new_question,

example_app/db/migrate/20130207214017_remove_questions_type.rb

@@ -0,0 +1,16 @@
+class RemoveQuestionsType < ActiveRecord::Migration
+  def up
+    remove_column :questions, :type
+  end
+
+  def down
+    add_column :questions, :type, :string
+
+    connection.update(<<-SQL)
+      UPDATE questions
+      SET type = REPLACE(submittable_type, 'Submittable', 'Question')
+    SQL
+
+    change_column_null :questions, :type, true
+  end
+end

example_app/db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20130207164259) do
+ActiveRecord::Schema.define(:version => 20130207214017) do
 
   create_table "answers", :force => true do |t|
     t.integer  "completion_id", :null => false
@@ -68,7 +68,6 @@
 
   create_table "questions", :force => true do |t|
     t.string   "title",            :null => false
-    t.string   "type",             :null => false
     t.integer  "survey_id",        :null => false
     t.datetime "created_at",       :null => false
     t.datetime "updated_at",       :null => false

example_app/spec/factories/application.rb

@@ -29,19 +29,20 @@
     text 'Hello'
   end
 
-  factory :question, class: 'OpenQuestion' do
-    survey
+  factory :question do
     sequence(:title) { |n| "Question #{n}" }
+    submittable factory: :open_submittable
+    survey
 
-    factory :multiple_choice_question, class: 'MultipleChoiceQuestion' do
+    factory :multiple_choice_question do
       submittable factory: :multiple_choice_submittable
     end
 
-    factory :open_question, class: 'OpenQuestion' do
+    factory :open_question do
       submittable factory: :open_submittable
     end
 
-    factory :scale_question, class: 'ScaleQuestion' do
+    factory :scale_question do
       submittable factory: :scale_submittable
     end
   end

example_app/spec/models/question_spec.rb

@@ -1,13 +1,13 @@
 require 'spec_helper'
 
 describe Question do
-  it { should validate_presence_of :type }
+  it { should validate_presence_of :submittable_type }
 
   Question::QUESTION_TYPES.each do |type|
-    it { should allow_value(type).for(:type) }
+    it { should allow_value(type).for(:submittable_type) }
   end
 
-  it { should_not allow_value('Other').for(:type) }
+  it { should_not allow_value('Other').for(:submittable_type) }
 
   it { should validate_presence_of :title }
 
@@ -71,7 +71,6 @@
       { minimum: 1, maximum: 2 })
 
     new_question.errors.should be_empty
-    new_question.should be_a(ScaleQuestion)
     submittable = new_question.submittable
     submittable.should be_a(ScaleSubmittable)
     submittable.minimum.should eq 1
@@ -85,7 +84,6 @@
     new_question = question.switch_to('ScaleQuestion', {}, { minimum: 1 })
 
     new_question.errors.should be_present
-    new_question.should be_a(ScaleQuestion)
     new_question.submittable.should be_a(ScaleSubmittable)
     new_question.submittable.minimum.should eq 1
   end

example_app/spec/support/features/survey_taker.rb

@@ -23,10 +23,10 @@ def start
 
   def answer(question_title, answer_text)
     question = Question.find_by_title!(question_title)
-    case question
-    when OpenQuestion
+    case question.submittable
+    when OpenSubmittable
       fill_in question_title, with: answer_text
-    when ScaleQuestion, MultipleChoiceQuestion
+    when ScaleSubmittable, MultipleChoiceSubmittable
       within %{li:contains("#{question_title}")} do
         choose answer_text
       end