Merge pull request #1718 from cawpat/master

[SCALA-339] - Usage of val and def fields in traits

Author: dominiqueplante

build.sbt

@@ -119,6 +119,14 @@ lazy val scala_core_9 = (project in file("scala-core-modules/scala-core-9"))
     libraryDependencies += "org.scalatestplus" %% "scalacheck-1-17" % "3.2.18.0" % Test
   )
 
+lazy val scala_core_10 = (project in file("scala-core-modules/scala-core-10"))
+  .settings(
+    name := "scala-core-10",
+    libraryDependencies ++= scalaTestDeps,
+    scalaVersion := scala3Version,
+    libraryDependencies += "org.scalatestplus" %% "scalacheck-1-17" % "3.2.18.0" % Test
+  )
+
 lazy val scala_core_numbers =
   (project in file("scala-core-modules/scala-core-numbers"))
     .settings(

scala-core-modules/scala-core-10/README.md

@@ -0,0 +1 @@
+### Relevant Articles

scala-core-modules/scala-core-10/src/main/scala/com/baeldung/scala/valsintraits/ValInTraitExamples.scala

@@ -0,0 +1,39 @@
+package com.baeldung.scala.valsintraits
+
+import java.time.LocalDateTime
+
+object ValInTraitExamples {
+  trait CurrentTimePrinter {
+    val currentTime: LocalDateTime
+    def printCurrentTime(): Unit
+  }
+  object TimePrinterImpl extends CurrentTimePrinter {
+    override val currentTime: LocalDateTime = LocalDateTime.now()
+    override def printCurrentTime(): Unit = println(currentTime)
+  }
+
+  trait CurrentTimePrinterWithDef {
+    def currentTime: LocalDateTime
+    def printCurrentTime(): Unit
+  }
+  object TimePrinterWithDefImpl extends CurrentTimePrinterWithDef {
+    override def currentTime: LocalDateTime = LocalDateTime.now()
+    override def printCurrentTime(): Unit = println(currentTime)
+  }
+
+  trait TraitA {
+    val multiplier: Int
+    val result: Int = multiplier * 7
+  }
+  trait TraitB {
+    val multiplier: Int = 10
+  }
+  trait TraitAWithDef {
+    val multiplier: Int
+    def result: Int = multiplier * 7
+  }
+
+  object AB extends TraitA with TraitB
+  object BA extends TraitB with TraitA
+  object ABWithDef extends TraitAWithDef with TraitB
+}

scala-core-modules/scala-core-10/src/test/scala/com/baeldung/scala/ValInTraitExamplesUnitTest.scala

@@ -0,0 +1,40 @@
+package com.baeldung.scala
+
+import com.baeldung.scala.valsintraits.ValInTraitExamples
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class ValInTraitExamplesUnitTest extends AnyFlatSpec with Matchers {
+  "TimePrinterImpl" should "return same time every call" in {
+    val printer = ValInTraitExamples.TimePrinterImpl
+    val first = printer.currentTime
+    Thread.sleep(10)
+    val second = printer.currentTime
+
+    first.shouldBe(second)
+  }
+
+  "TimePrinterWithDefImpl" should "return different time every call" in {
+    val printer = ValInTraitExamples.TimePrinterWithDefImpl
+    val first = printer.currentTime
+    Thread.sleep(10)
+    val second = printer.currentTime
+
+    first should not be second
+  }
+
+  "ClassAB" should "return result as 0" in {
+    val classAb = ValInTraitExamples.AB
+    classAb.result shouldBe 0
+  }
+
+  "ClassBA" should "return result as 70" in {
+    val classBa = ValInTraitExamples.BA
+    classBa.result shouldBe 70
+  }
+
+  "ClassABWithDef" should "return result as 70" in {
+    val classAbWithDef = ValInTraitExamples.ABWithDef
+    classAbWithDef.result shouldBe 70
+  }
+}