add some good stuff!

lib/iron_trail/change_model_concern.rb

@@ -8,6 +8,10 @@ def reify
       Reifier.reify(self)
     end
 
+    def insert_operation? = (operation == 'i')
+    def update_operation? = (operation == 'u')
+    def delete_operation? = (operation == 'd')
+
     module ClassMethods
       def where_object_changes_to(args = {})
         _where_object_changes(1, args)

lib/iron_trail/reifier.rb

@@ -3,10 +3,10 @@
 module IronTrail
   module Reifier
     def self.reify(trail)
-      klass = model_from_table_name(trail.rec_table)
+      source_attributes = (trail.delete_operation? ? trail.rec_old : trail.rec_new)
+      klass = model_from_table_name(trail.rec_table, source_attributes['type'])
 
       record = klass.where(id: trail.rec_id).first || klass.new
-      source_attributes = (trail.operation == 'd' ? trail.rec_old : trail.rec_new)
 
       source_attributes.each do |name, value|
         if record.has_attribute?(name)
@@ -26,13 +26,27 @@ def self.reify(trail)
       record
     end
 
-    def self.model_from_table_name(table_name)
-      # TODO: this won't work with STI models.
-      index = ActiveRecord::Base.descendants.reject(&:abstract_class).index_by(&:table_name)
+    def self.model_from_table_name(table_name, sti_type=nil)
+      index = ActiveRecord::Base.descendants.reject(&:abstract_class).chunk(&:table_name).to_h do |key, val|
+        v = \
+          if val.length == 1
+            val[0]
+          else
+            val.to_h { |k| [k.to_s, k] }
+          end
+
+        [key, v]
+      end
+
       klass = index[table_name]
       raise "Cannot infer model from table named '#{table_name}'" unless klass
 
-      klass
+      return klass unless klass.is_a?(Hash)
+      klass = klass[sti_type]
+
+      return klass if klass
+
+      raise "Cannot infer STI model for table #{table_name} and type '#{sti_type}'"
     end
   end
 end

spec/dummy_app/app/models/irontrail_change.rb

@@ -5,4 +5,8 @@ class IrontrailChange < ApplicationRecord
   include IronTrail::ChangeModelConcern
 
   range_partition_by { :created_at }
+
+  scope :inserts, -> { where(operation: 'i') }
+  scope :updates, -> { where(operation: 'u') }
+  scope :deletes, -> { where(operation: 'd') }
 end

spec/dummy_app/app/models/matrix_pill.rb

@@ -2,4 +2,5 @@
 
 # An STI model
 class MatrixPill < ApplicationRecord
+  include IronTrail::Model
 end

spec/dummy_app/app/services/morpheus.rb

@@ -4,12 +4,8 @@
 class Morpheus
   def just_like_in_the_movie
     {
-      red: RedPill.create!,
-      blue: PillBlue.create!
+      red: RedPill.create!(pill_size: 10),
+      blue: PillBlue.create!(pill_size: 11)
     }
   end
-
-  def guitar_hero
-  end
-
 end

spec/models/guitar_spec.rb

@@ -3,6 +3,38 @@
 RSpec.describe Guitar do
   let(:person) { Person.create!(first_name: 'Arthur', last_name: 'Schopenhauer') }
 
+  describe 'IronTrail::ChangeModelConcern' do
+    describe 'helper methods' do
+      before do
+        person.update!(first_name: 'Joe')
+        person.update!(first_name: 'Joey')
+        person.destroy!
+      end
+
+      it 'correctly classifies operations' do
+        expect(person.iron_trails.length).to eq(4)
+        expect(person.iron_trails.inserts.length).to eq(1)
+        expect(person.iron_trails.updates.length).to eq(2)
+        expect(person.iron_trails.deletes.length).to eq(1)
+
+        expect(person.iron_trails.inserts[0].insert_operation?).to be(true)
+        expect(person.iron_trails.inserts[0].update_operation?).to be(false)
+        expect(person.iron_trails.inserts[0].delete_operation?).to be(false)
+
+        expect(person.iron_trails.updates[0].insert_operation?).to be(false)
+        expect(person.iron_trails.updates[0].update_operation?).to be(true)
+        expect(person.iron_trails.updates[0].delete_operation?).to be(false)
+        expect(person.iron_trails.updates[1].insert_operation?).to be(false)
+        expect(person.iron_trails.updates[1].update_operation?).to be(true)
+        expect(person.iron_trails.updates[1].delete_operation?).to be(false)
+
+        expect(person.iron_trails.deletes[0].insert_operation?).to be(false)
+        expect(person.iron_trails.deletes[0].update_operation?).to be(false)
+        expect(person.iron_trails.deletes[0].delete_operation?).to be(true)
+      end
+    end
+  end
+
   describe 'iron_trails.version_at' do
     let(:guitar) { Guitar.create!(description: 'the guitar', person:) }
 

spec/services/morpheus_spec.rb

@@ -2,12 +2,37 @@
 
 RSpec.describe Morpheus do
   subject(:instance) { described_class.new }
+  subject(:pills) { instance.just_like_in_the_movie }
 
-  describe '#just_like_in_the_movie' do
-    xit 'offers two pills' do
-      3.times { described_class.new.just_like_in_the_movie }
+  it 'has the type attribute serialized' do
+    red = pills[:red]
 
-      pills = described_class.new.just_like_in_the_movie
+    red.update!(pill_size: 44)
+    trails = red.reload.iron_trails.order(id: :asc)
+
+    expect(trails.length).to eq(2)
+    expect(trails[0].rec_new['type']).to eq('RedPill')
+    expect(trails[1].rec_new['type']).to eq('RedPill')
+  end
+
+  describe 'object morphing' do
+    it 'morphs colors' do
+      blue = pills[:blue]
+      pills[:red].destroy!
+
+      blue.update!(pill_size: 15)
+      blue.update!(pill_size: 25)
+
+      trail = blue.iron_trails.where_object_changes_to(pill_size: 15).first
+      trail.rec_new['type'] = 'RedPill' # likely invalid case in the real world, but good for testing.
+      trail.save!
+      blue.reload
+
+      red = blue.iron_trails.where_object_changes_to(pill_size: 15).first.reify
+      expect(red).to be_a(RedPill)
+
+      blue_again = blue.iron_trails.where_object_changes_to(pill_size: 25).first.reify
+      expect(blue_again).to be_a(PillBlue)
     end
   end
 end