Introduction to traits

core-scala/src/main/scala/com/baeldung/scala/traits/Composition.scala

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+package com.baeldung.scala.traits
+
+trait Composition extends Orchestration with Mixing {
+  var composer: String
+
+  def compose(): String
+
+  var studio: String
+
+  def getStudio(): String = s"Composed at studio $studio"
+}

core-scala/src/main/scala/com/baeldung/scala/traits/Mixing.scala

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+package com.baeldung.scala.traits
+
+trait Mixing {
+  var mixer: String
+  val qualityRatio: Double = 3.14
+
+  def algorithm: MixingAlgorithm = HighInstrumentalQuality
+}

core-scala/src/main/scala/com/baeldung/scala/traits/MixingAlgorithm.scala

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+package com.baeldung.scala.traits
+
+sealed trait MixingAlgorithm
+
+case object LowInstrumentalQuality extends MixingAlgorithm {
+  override def toString(): String = "Low instrumental quality"
+}
+
+case object HighInstrumentalQuality extends MixingAlgorithm {
+  override def toString(): String = "High instrumental quality"
+}

core-scala/src/main/scala/com/baeldung/scala/traits/Orchestration.scala

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+package com.baeldung.scala.traits
+
+trait Orchestration {
+  var orchestra: String
+}

core-scala/src/main/scala/com/baeldung/scala/traits/RecordLabel.scala

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+package com.baeldung.scala.traits
+
+class RecordLabel

core-scala/src/main/scala/com/baeldung/scala/traits/Score.scala

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+package com.baeldung.scala.traits
+
+class Score(var composer: String,
+            var engineer: String,
+            var orchestra: String,
+            var mixer: String,
+            override val qualityRatio: Double,
+            var studio: String)
+  extends RecordLabel with Composition with SoundProduction {
+
+  override def compose(): String =
+    s"""The score is composed by $composer,
+       |Orchestration by $orchestra,
+       |Mixed by $mixer""".stripMargin
+
+  override def produce(): String = s"The score is produced by $engineer"
+
+  override def algorithm(): MixingAlgorithm = {
+    if (qualityRatio < 3) LowInstrumentalQuality
+    else super.algorithm
+  }
+
+  override def getStudio(): String =
+    super[Composition].getStudio() + ", " + super[SoundProduction].getStudio()
+}

core-scala/src/main/scala/com/baeldung/scala/traits/SoundProduction.scala

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+package com.baeldung.scala.traits
+
+trait SoundProduction {
+  this: RecordLabel =>
+  var engineer: String
+
+  def produce(): String
+
+  var studio: String
+
+  def getStudio(): String = s"Produced at studio $studio"
+}

core-scala/src/main/scala/com/baeldung/scala/traits/Vocals.scala

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+package com.baeldung.scala.traits
+
+trait Vocals {
+  val sing: String = "Vocals mixin"
+}

core-scala/src/test/scala/com/baeldung/scala/traits/ScoreUnitTest.scala

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+package com.baeldung.scala.traits
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class ScoreUnitTest {
+
+  @Test
+  def givenScore_whenComposeCalled_thenCompositionIsReturned() = {
+
+    val composer = "Hans Zimmer"
+    val engineer = "Matt Dunkley"
+    val orchestra = "Berlin Philharmonic"
+    val mixer = "Dave Stewart"
+    val studio = "Abbey Studios"
+    val score = new Score(composer, engineer, orchestra, mixer, 10, studio)
+
+    assertEquals(score.compose(),
+      s"""The score is composed by $composer,
+         |Orchestration by $orchestra,
+         |Mixed by $mixer""".stripMargin)
+  }
+
+  @Test
+  def givenScore_whenProduceCalled_thenSoundProductionIsReturned() = {
+
+    val composer = "Hans Zimmer"
+    val engineer = "Matt Dunkley"
+    val orchestra = "Berlin Philharmonic"
+    val mixer = "Dave Stewart"
+    val studio = "Abbey Studios"
+    val score = new Score(composer, engineer, orchestra, mixer, 3, studio)
+
+    assertEquals(score.produce(), s"The score is produced by $engineer")
+  }
+
+  @Test
+  def givenScore_whenLowQualityRatioSet_thenCorrectAlgorithmIsReturned() = {
+
+    val composer = "Hans Zimmer"
+    val engineer = "Matt Dunkley"
+    val orchestra = "Berlin Philharmonic"
+    val mixer = "Dave Stewart"
+    val studio = "Abbey Studios"
+    val score = new Score(composer, engineer, orchestra, mixer, 1, studio)
+
+    assertEquals(score.algorithm().toString, "Low instrumental quality")
+  }
+
+  @Test
+  def givenScore_whenHighQualityRatioSet_thenCorrectAlgorithmIsReturned() = {
+
+    val composer = "Hans Zimmer"
+    val engineer = "Matt Dunkley"
+    val orchestra = "Berlin Philharmonic"
+    val mixer = "Dave Stewart"
+    val studio = "Abbey Studios"
+    val score = new Score(composer, engineer, orchestra, mixer, 10, studio)
+
+    assertEquals(score.algorithm().toString, "High instrumental quality")
+  }
+
+  @Test
+  def givenScore_whenVocalsMixinAttached_thenSingCanBeCalled() = {
+
+    val composer = "Hans Zimmer"
+    val engineer = "Matt Dunkley"
+    val orchestra = "Berlin Philharmonic"
+    val mixer = "Dave Stewart"
+    val studio = "Abbey Studios"
+    val score = new Score(composer, engineer, orchestra, mixer, 10, studio) with Vocals
+
+    assertEquals(score.sing, "Vocals mixin")
+  }
+
+  @Test
+  def givenScore_whenGetStudioCalled_thenStudiosAreReturned() = {
+
+    val composer = "Hans Zimmer"
+    val engineer = "Matt Dunkley"
+    val orchestra = "Berlin Philharmonic"
+    val mixer = "Dave Stewart"
+    val studio = "Abbey Studios"
+    val score = new Score(composer, engineer, orchestra, mixer, 10, studio)
+
+    assertEquals(
+      score.getStudio(),
+      s"Composed at studio $studio, Produced at studio $studio"
+    )
+  }
+}