Original drafted 17 March 2014 for an incomplete article. <\/p>\n
The Cake pattern for Scala using a flaming cake as well. <\/p>\n
This is the quasi-production code:<\/p>\n
\r\npackage uk.co.xenonique.learning.cake\r\n\r\n\/**\r\n * The type Cake\r\n *\r\n * @author Peter Pilgrim\r\n *\/\r\nclass Cake(val name: String) {\r\n def inspect(): String = {\r\n name\r\n }\r\n}\r\n\r\ntrait Oven {\r\n def powerUp(): Unit\r\n def powerDown(): Unit\r\n\r\n}\r\ntrait CakeMaker {\r\n def bake( cake: Cake )\r\n}\r\n\r\ntrait CakeFactory {\r\n def produce( cakes: List[Cake] )\r\n}\r\n\r\nclass CakeFactoryImpl extends CakeFactory {\r\n this: CakeMaker with Oven =>\r\n override def produce( cakes: List[Cake] ): Unit = {\r\n powerUp()\r\n for ( c <- cakes) {\r\n bake(c)\r\n }\r\n powerDown()\r\n }\r\n}\r\n<\/pre>\nThis is the learning test code:<\/p>\n
\r\npackage uk.co.xenonique.learning.cake\r\n\r\nimport org.scalatest.WordSpec\r\nimport org.scalatest.matchers.MustMatchers\r\nimport org.scalatest.mock.MockitoSugar\r\n\/**\r\n * The type CakeSpec\r\n *\r\n * @author Peter Pilgrim\r\n *\/\r\nclass CakeSpec extends WordSpec with MockitoSugar with MustMatchers {\r\n\r\n trait Baker extends CakeMaker {\r\n override def bake(cake: Cake): Unit = {\r\n println(s"I'm a baker, baking a cake: "+cake.inspect())\r\n }\r\n }\r\n\r\n trait IndustrialOven extends Oven {\r\n override def powerUp() = {\r\n println("firing up the oven")\r\n }\r\n override def powerDown() = {\r\n println("venting the oven")\r\n }\r\n }\r\n\r\n "Cake" should {\r\n "understand the cake pattern" in {\r\n val factory = new CakeFactoryImpl() with Baker with IndustrialOven {\r\n }\r\n val cakes = List( new Cake("Battenburg"), new Cake("Cherry Madeira"), new Cake("Lemon and Lime"))\r\n factory.produce(cakes)\r\n }\r\n }\r\n}\r\n<\/pre>\nAssuming that you know what you are doing: insert this code into a test Scala project with a decent IDE. Run the test should demonstrate the results.<\/p>\n
What is the benefit of this so-called Cake Pattern? Well in short, Scala allows self-type with multiple traits (the dependencies). See the definition of CakeFactoryImpl<\/code>, which expresses a dependency on the type CakeMaker and an Oven traits being mixed-in to the final concrete class. In other words, the final CakeFactoryImpl<\/code> is a type of CakeMaker<\/code> (Baker<\/code>) and also it is type of Oven<\/code> (IndustrialOven<\/code>). Therefore, it is a small exercise to write mock objects with these traits, hence the reason I demonstrated with the pattern using a ScalaTest. In fact, it is an exercise to the reader, to write Mockito mocks of this CakeFactoryImpl. Imagine if your Oven was a reference, wrapper or connection pool to a database.<\/p>\nFinally, to understand the cake pattern you have to comprehend the Scala self-types and annotations. Personally, I found this pattern a little convoluted, because of the traits tend to have partial implementations in a production work. <\/p>\n","protected":false},"excerpt":{"rendered":"
Original drafted 17 March 2014 for an incomplete article. The Cake pattern for Scala using a flaming cake as well. This is the quasi-production code: This is the learning test code: Assuming that you know what you are doing: insert this code into a test Scala project with a decent IDE. Run the test should […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[123,75,172,40,6,52],"tags":[],"_links":{"self":[{"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/posts\/1554"}],"collection":[{"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/comments?post=1554"}],"version-history":[{"count":3,"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/posts\/1554\/revisions"}],"predecessor-version":[{"id":1573,"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/posts\/1554\/revisions\/1573"}],"wp:attachment":[{"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/media?parent=1554"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/categories?post=1554"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.xenonique.co.uk\/blog\/wp-json\/wp\/v2\/tags?post=1554"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}