Replace Subclasses with Strategies: Step Fifteen

* Simplify type switching

Author: jferris

example_app/app/controllers/types_controller.rb

@@ -1,37 +1,25 @@
 class TypesController < ApplicationController
   def new
     @question = Question.find(params[:question_id])
-    assign_type
-    @new_question = Question.new
-    @new_question.build_submittable(type, {})
+    @question.build_submittable(type, {})
   end
 
   def create
     @question = Question.find(params[:question_id])
-    @new_question = @question.switch_to(
+    @question.switch_to(
       type,
-      question_params,
       submittable_attributes
     )
 
-    if @new_question.errors.empty?
+    if @question.errors.empty?
       redirect_to @question.survey
     else
-      assign_type
       render 'new'
     end
   end
 
   private
 
-  def assign_type
-    @new_type = type.underscore
-  end
-
-  def question_params
-    params[:question].except(:submittable_attributes)
-  end
-
   def submittable_attributes
     params[:question][:submittable_attributes] || {}
   end

example_app/app/models/question.rb

@@ -34,21 +34,14 @@ def summarize(summarizer)
     Summary.new(title, value)
   end
 
-  def switch_to(type, new_attributes, submittable_attributes)
-    attributes = self.attributes.merge(new_attributes)
-    cloned_attributes = attributes.except('id', 'type', 'submittable_type')
-    new_question = Question.new(cloned_attributes)
-    new_question.build_submittable(type, submittable_attributes)
-    new_question.id = id
-
-    begin
-      Question.transaction do
-        destroy
-        new_question.save!
+  def switch_to(type, attributes)
+    old_submittable = submittable
+    build_submittable type, attributes
+
+    transaction do
+      if save
+        old_submittable.destroy
       end
-    rescue ActiveRecord::RecordInvalid
     end
-
-    new_question
   end
 end

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

@@ -1,13 +1,14 @@
 <%= simple_form_for(
-  @new_question,
+  @question,
   as: :question,
-  url: question_types_path(@question)
+  url: question_types_path(@question),
+  method: :post
 ) do |form| -%>
 
   <%= form.hidden_field :submittable_type %>
   <%= render(
-    "#{@new_type}s/#{@new_type}_form",
-    question: @new_question,
+    "#{@question.submittable.to_partial_path}_form",
+    submittable: @question.submittable,
     form: form
   ) %>
   <%= form.submit 'Change Type' %>

example_app/spec/models/question_spec.rb

@@ -65,26 +65,27 @@
   it 'changes the question type and deletes the old question when valid' do
     question = create(:open_question)
 
-    new_question = question.switch_to(
+    question.switch_to(
       'ScaleQuestion',
-      {},
-      { minimum: 1, maximum: 2 })
+      { minimum: 1, maximum: 2 }
+    )
 
-    new_question.errors.should be_empty
-    submittable = new_question.submittable
+    question.errors.should be_empty
+    submittable = question.submittable
     submittable.should be_a(ScaleSubmittable)
     submittable.minimum.should eq 1
     submittable.maximum.should eq 2
     Question.count.should eq 1
+    OpenSubmittable.count.should eq 0
   end
 
   it 'leaves the question alone when the new attributes are invalid' do
     question = create(:open_question)
 
-    new_question = question.switch_to('ScaleQuestion', {}, { minimum: 1 })
+    question.switch_to('ScaleQuestion', { minimum: 1 })
 
-    new_question.errors.should be_present
-    new_question.submittable.should be_a(ScaleSubmittable)
-    new_question.submittable.minimum.should eq 1
+    question.errors.should be_present
+    question.submittable.should be_a(ScaleSubmittable)
+    question.submittable.minimum.should eq 1
   end
 end