Added DataObjects::Schema::Transformable#transform_unless

do-schema.gemspec

@@ -120,7 +120,9 @@ Gem::Specification.new do |s|
      "spec/unit/data_objects/schema/tables/initialize_spec.rb",
      "spec/unit/data_objects/schema/tables/length_spec.rb",
      "spec/unit/data_objects/schema/tables/merge_spec.rb",
+     "spec/unit/data_objects/schema/transformable/fixtures/dummy.rb",
      "spec/unit/data_objects/schema/transformable/transform_spec.rb",
+     "spec/unit/data_objects/schema/transformable/transform_unless_spec.rb",
      "tasks/ci.rake",
      "tasks/clean.rake",
      "tasks/quality/flay.rake",
@@ -213,7 +215,9 @@ Gem::Specification.new do |s|
      "spec/unit/data_objects/schema/tables/initialize_spec.rb",
      "spec/unit/data_objects/schema/tables/length_spec.rb",
      "spec/unit/data_objects/schema/tables/merge_spec.rb",
-     "spec/unit/data_objects/schema/transformable/transform_spec.rb"
+     "spec/unit/data_objects/schema/transformable/fixtures/dummy.rb",
+     "spec/unit/data_objects/schema/transformable/transform_spec.rb",
+     "spec/unit/data_objects/schema/transformable/transform_unless_spec.rb"
   ]
 
   if s.respond_to? :specification_version then

lib/do-schema/support/transformable.rb

@@ -11,6 +11,10 @@ def transform(&block)
         copy.freeze
       end
 
+      def transform_unless(condition, &block)
+        condition ? self : transform(&block)
+      end
+
     end # module Transformable
 
   end # module Schema

spec/unit/data_objects/schema/transformable/fixtures/dummy.rb

@@ -0,0 +1,23 @@
+require 'do-schema/support/transformable'
+
+class Immutable
+
+  include DataObjects::Schema::Transformable
+
+  attr_reader :state, :delta
+
+  def initialize(state)
+    @state = state
+    @delta = nil
+  end
+
+  def modify(delta)
+    transform { @delta = delta }
+  end
+
+  def modify_unless(condition, delta)
+    transform_unless(condition) { @delta = delta }
+  end
+
+end
+

spec/unit/data_objects/schema/transformable/transform_spec.rb

@@ -1,22 +1,6 @@
 require 'spec_helper'
 require 'do-schema/support/transformable'
-
-class Immutable
-
-  include DataObjects::Schema::Transformable
-
-  attr_reader :state, :delta
-
-  def initialize(state)
-    @state = state
-    @delta = nil
-  end
-
-  def modify(delta)
-    transform { @delta = delta }
-  end
-
-end
+require 'spec/unit/data_objects/schema/transformable/fixtures/dummy'
 
 describe 'DataObjects::Schema::Transformable#transform' do
 

spec/unit/data_objects/schema/transformable/transform_unless_spec.rb

@@ -0,0 +1,38 @@
+require 'spec_helper'
+require 'do-schema/support/transformable'
+require 'spec/unit/data_objects/schema/transformable/fixtures/dummy'
+
+describe 'DataObjects::Schema::Transformable#transform_unless' do
+
+  let(:instance) { Immutable.new(state) }
+  let(:state)    { 'foo'                }
+  let(:delta)    { 'baz'                }
+
+  context 'when the condition evaluates to true' do
+
+    subject { instance.modify_unless(true, delta) }
+
+    it { should equal(instance) }
+    it { should_not be_frozen   }
+
+    its(:state) { should == state }
+    its(:delta) { should == nil }
+
+  end
+
+  context 'when the condition evaluates to false' do
+
+    subject { instance.modify_unless(false, delta) }
+
+    it { should_not equal(instance)       }
+    it { should be_instance_of(Immutable) }
+    it { should be_frozen                 }
+
+    its(:state) { should == state }
+    its(:delta) { should == delta }
+
+  end
+
+end
+
+