Generate uuid after initialize to support validations on id

lib/activeuuid/uuid.rb

@@ -86,6 +86,7 @@ module UUID
 
       singleton_class.alias_method_chain :instantiate, :uuid
       before_create :generate_uuids_if_needed
+      after_initialize :generate_uuids_if_needed
     end
 
     module ClassMethods

spec/lib/activerecord_spec.rb

@@ -96,6 +96,28 @@
   let(:model) { described_class }
   subject { model }
 
+  context 'new record' do
+    let!(:article) { Fabricate.build :uuid_article }
+    subject { article }
+    let(:uuid) { UUIDTools::UUID.random_create }
+    let(:string) { uuid.to_s }
+    before { subject.another_uuid = string }
+
+    context 'validation' do
+      its(:id) { should be_nil }
+      its(:another_uuid) { should be_a UUIDTools::UUID  }
+      specify { subject.should be_new_record }
+      specify { subject.should be_valid }
+    end
+
+    context 'save without validation' do
+      before { subject.save(validate: false) }
+
+      its(:id) { should be_a UUIDTools::UUID }
+      specify { subject.should be_valid }
+    end
+  end
+
   context 'model' do
     its(:primary_key) { should == 'id' }
     its(:all) { should == [article] }
@@ -184,4 +206,4 @@
       end
     end
   end
-end
+end

spec/support/models/uuid_article.rb

@@ -1,3 +1,7 @@
 class UuidArticle < ActiveRecord::Base
   include ActiveUUID::UUID
+
+  validates :id, presence: true, uniqueness: true, length: { in: 32..40 }, unless: :new_record?
+  validates :another_uuid, presence: true, uniqueness: true, length: { in: 32..40 }, unless: :new_record?
+
 end