Traits Examples

Traits example:

cala> println("Step 1: Create a trait which will define the methods for a data access layer")

Step 1: Create a trait which will define the methods for a data access layer

scala> trait DonutShoppingCartDao {
     |
     |  def add(donutName: String): Long
     |
     |  def update(donutName: String): Boolean
     |
     |  def search(donutName: String): String
     |
     |  def delete(donutName: String): Boolean
     |
     |  }
defined trait DonutShoppingCartDao

scala> println("\nStep 2: Create a DonutShoppingCart class which extends the trait from Step 1 and implements its methods")

Step 2: Create a DonutShoppingCart class which extends the trait from Step 1 and implements its methods

scala> class DonutShoppingCart extends DonutShoppingCartDao {
     |
     |  override def add(donutName: String): Long = {
     |   println(s"DonutShoppingCart-> add method -> donutName: $donutName")
     |   1
     |  }
     |
     |  override def update(donutName: String): Boolean = {
     |   println(s"DonutShoppingCart-> update method -> donutName: $donutName")
     |   true
     |  }
     |
     |  override def search(donutName: String): String = {
     |   println(s"DonutShoppingCart-> search method -> donutName: $donutName")
     |   donutName
     |  }
     |
     |  override def delete(donutName: String): Boolean = {
     |   println(s"DonutShoppingCart-> delete method -> donutName: $donutName")
     |   true
     |  }
     | }
defined class DonutShoppingCart


scala>
scala> println("\nStep 3: Create an instance of DonutShoppingCart and call the add, update, search and delete methods")


Step 3: Create an instance of DonutShoppingCart and call the add, update, search and delete methods

scala> val donutShoppingCart1: DonutShoppingCart = new DonutShoppingCart()
donutShoppingCart1: DonutShoppingCart = DonutShoppingCart@2cb6bc65

scala> donutShoppingCart1.add("Vanilla Donut")
DonutShoppingCart-> add method -> donutName: Vanilla Donut
res52: Long = 1

scala> donutShoppingCart1.update("Vanilla Donut")
DonutShoppingCart-> update method -> donutName: Vanilla Donut
res53: Boolean = true

scala> donutShoppingCart1.search("Vanilla Donut")
DonutShoppingCart-> search method -> donutName: Vanilla Donut
res54: String = Vanilla Donut

scala> donutShoppingCart1.delete("Vanilla Donut")
DonutShoppingCart-> delete method -> donutName: Vanilla Donut
res55: Boolean = true

scala> println("\nStep 4: Create an instance of DonutShoppingCart and assign its type to the trait DonutShoppingCartDao")

Step 4: Create an instance of DonutShoppingCart and assign its type to the trait DonutShoppingCartDao

scala> val donutShoppingCart2: DonutShoppingCartDao = new DonutShoppingCart()
donutShoppingCart2: DonutShoppingCartDao = DonutShoppingCart@1f24fb1

scala> donutShoppingCart2.add("Vanilla Donut")
DonutShoppingCart-> add method -> donutName: Vanilla Donut
res57: Long = 1

scala> donutShoppingCart2.update("Vanilla Donut")
DonutShoppingCart-> update method -> donutName: Vanilla Donut
res58: Boolean = true

scala> donutShoppingCart2.search("Vanilla Donut")
DonutShoppingCart-> search method -> donutName: Vanilla Donut
res59: String = Vanilla Donut

scala> donutShoppingCart2.delete("Vanilla Donut")
DonutShoppingCart-> delete method -> donutName: Vanilla Donut
res60: Boolean = true


val donutShoppingCart2: DonutShoppingCartDao[String] = new DonutShoppingCart[String]()
donutShoppingCart2.add("Vanilla Donut")
donutShoppingCart2.update("Vanilla Donut")
donutShoppingCart2.search("Vanilla Donut")
donutShoppingCart2.delete("Vanilla Donut")


scala> trait DonutShoppingCartDao[A] {
     |
     |  def add(donut: A): Long
     |
     |  def update(donut: A): Boolean
     |
     |  def search(donut: A): A
     |
     |  def delete(donut: A): Boolean
     |
     | }
defined trait DonutShoppingCartDao


scala> println("\nStep 2: Create a second trait which will define the methods for checking donut inventory")

Step 2: Create a second trait which will define the methods for checking donut inventory
scala> trait DonutInventoryService[A] {
     |
     |  def checkStockQuantity(donut: A): Int
     |
     | }
defined trait DonutInventoryService


scala>
scala> println("\nStep 3: Create a DonutShoppingCart class which extends multiple traits namely trait DonutShoppingCartDao and trait DonutInventoryService")

Step 3: Create a DonutShoppingCart class which extends multiple traits namely trait DonutShoppingCartDao and trait DonutInventoryService

scala> class DonutShoppingCart[A] extends DonutShoppingCartDao[A] with DonutInventoryService[A] {
     |
     |  override def add(donut: A): Long = {
     |   println(s"DonutShoppingCart-> add method -> donut: $donut")
     |   1
     |  }
     |
     |  override def update(donut: A): Boolean = {
     |   println(s"DonutShoppingCart-> update method -> donut: $donut")
     |   true
     |  }
     |
     |  override def search(donut: A): A = {
     |   println(s"DonutShoppingCart-> search method -> donut: $donut")
     |   donut
     |  }
     |
     |  override def delete(donut: A): Boolean = {
     |   println(s"DonutShoppingCart-> delete method -> donut: $donut")
     |   true
     |  }
     |
     |  override def checkStockQuantity(donut: A): Int = {
     |   println(s"DonutShoppingCart-> checkStockQuantity method -> donut: $donut")
     |   10
     |  }
     | }
defined class DonutShoppingCart

scala> println("\nStep 4: Create an instance of DonutShoppingCart and call the add, update, search and delete methods")

Step 4: Create an instance of DonutShoppingCart and call the add, update, search and delete methods
scala> val donutShoppingCart: DonutShoppingCart[String] = new DonutShoppingCart[String]()
donutShoppingCart: DonutShoppingCart[String] = DonutShoppingCart@7bd395f7

scala> donutShoppingCart.add("Vanilla Donut")
DonutShoppingCart-> add method -> donut: Vanilla Donut
res73: Long = 1

scala> donutShoppingCart.update("Vanilla Donut")
DonutShoppingCart-> update method -> donut: Vanilla Donut
res74: Boolean = true

scala> donutShoppingCart.search("Vanilla Donut")
DonutShoppingCart-> search method -> donut: Vanilla Donut
res75: String = Vanilla Donut

scala> donutShoppingCart.delete("Vanilla Donut")
DonutShoppingCart-> delete method -> donut: Vanilla Donut
res76: Boolean = true

scala> println("\nStep 5: Call the checkStockQuantity method which was inherited from trait DonutInventoryService")


Step 5: Call the checkStockQuantity method which was inherited from trait DonutInventoryService

scala> donutShoppingCart.checkStockQuantity("Vanilla Donut")
DonutShoppingCart-> checkStockQuantity method -> donut: Vanilla Donut
res78: Int = 10

scala>
cala> trait DonutDatabase[A] {
     |
     |  def addOrUpdate(donut: A): Long
     |
     |  def query(donut: A): A
     |
     |  def delete(donut: A): Boolean
     | }
defined trait DonutDatabase
scala>

scala> println("\nStep 2: Create a class which extends trait DonutDatabase and knows how to perform CRUD operations with Apache Cassandra as storage layer")

Step 2: Create a class which extends trait DonutDatabase and knows how to perform CRUD operations with Apache Cassandra as storage layer

scala> class CassandraDonutStore[A] extends DonutDatabase[A] {
     |
     |  override def addOrUpdate(donut: A): Long = {
     |   println(s"CassandraDonutDatabase-> addOrUpdate method -> donut: $donut")
     |   1
     |  }
     |
     |  override def query(donut: A): A = {
     |   println(s"CassandraDonutDatabase-> query method -> donut: $donut")
     |   donut
     |  }
     |
     |  override def delete(donut: A): Boolean = {
     |   println(s"CassandraDonutDatabase-> delete method -> donut: $donut")
     |   true
     |  }
     | }
defined class CassandraDonutStore

scala> println("\nStep 3: Create a trait which will define the methods for a data access layer and will require dependency injection for DonutDatabase


Step 3: Create a trait which will define the methods for a data access layer and will require dependency injection for DonutDatabase
scala> trait DonutShoppingCartDao[A] {
     |
     |  val donutDatabase: DonutDatabase[A] // dependency injection
     |
     |  def add(donut: A): Long = {
     |   println(s"DonutShoppingCartDao-> add method -> donut: $donut")
     |   donutDatabase.addOrUpdate(donut)
     |  }
     |
     |  def update(donut: A): Boolean = {
     |   println(s"DonutShoppingCartDao-> update method -> donut: $donut")
     |   donutDatabase.addOrUpdate(donut)
     |   true
     |  }
     |
     |  def search(donut: A): A = {
     |   println(s"DonutShoppingCartDao-> search method -> donut: $donut")
     |   donutDatabase.query(donut)
     |  }
     |
     |  def delete(donut: A): Boolean = {
     |   println(s"DonutShoppingCartDao-> delete method -> donut: $donut")
     |   donutDatabase.delete(donut)
     |  }
     |
     | }
defined trait DonutShoppingCartDao

scala> println("\nStep 4: Create a trait which will define the methods for checking donut inventory and will require dependency injection for DonutDatabase")


Step 4: Create a trait which will define the methods for checking donut inventory and will require dependency injection for DonutDatabase

scala> trait DonutInventoryService[A] {
     |
     |  val donutDatabase: DonutDatabase[A] // dependency injection
     |
     |  def checkStockQuantity(donut: A): Int = {
     |   println(s"DonutInventoryService-> checkStockQuantity method -> donut: $donut")
     |   donutDatabase.query(donut)
     |   1
     |  }
     |
     | }
defined trait DonutInventoryService

scala> println("\nStep 5: Create a trait which will act as a facade which extends multiple traits namely trait DonutShoppingCartDao and trait DonutInventoryService. It also inject the correct DonutDatabase implementation - a CassandraDonutStore")

Step 5: Create a trait which will act as a facade which extends multiple traits namely trait DonutShoppingCartDao and trait DonutInventoryService. It also inject the correct DonutDatabase implementation - a CassandraDonutStore

scala> trait DonutShoppingCartServices[A] extends DonutShoppingCartDao[A] with DonutInventoryService[A] {
     |  override val donutDatabase: DonutDatabase[A] = new CassandraDonutStore[A]()
     | }
defined trait DonutShoppingCartServices


scala> println("\nStep 6: Create a DonutShoppingCart class which extends a single facade named DonutShoppingCartServices to expose all the underlying features required by a DonutShoppingCart")



Step 6: Create a DonutShoppingCart class which extends a single facade named DonutShoppingCartServices to expose all the underlying features required by a DonutShoppingCart
scala>  class DonutShoppingCart[A] extends DonutShoppingCartServices[A] {
     |
     | }
defined class DonutShoppingCart


scala> println("\nStep 7: Create an instance of DonutShoppingCart and call the add, update, search and delete methods")


Step 7: Create an instance of DonutShoppingCart and call the add, update, search and delete methods

scala> val donutShoppingCart: DonutShoppingCart[String] = new DonutShoppingCart[String]()
donutShoppingCart: DonutShoppingCart[String] = DonutShoppingCart@5a4be77f

scala> donutShoppingCart.add("Vanilla Donut")
DonutShoppingCartDao-> add method -> donut: Vanilla Donut

CassandraDonutDatabase-> addOrUpdate method -> donut: Vanilla Donut
res85: Long = 1
scala> donutShoppingCart.update("Vanilla Donut")

DonutShoppingCartDao-> update method -> donut: Vanilla Donut
CassandraDonutDatabase-> addOrUpdate method -> donut: Vanilla Donut
res86: Boolean = true

scala> donutShoppingCart.search("Vanilla Donut")
DonutShoppingCartDao-> search method -> donut: Vanilla Donut

CassandraDonutDatabase-> query method -> donut: Vanilla Donut
res87: String = Vanilla Donut

scala> donutShoppingCart.delete("Vanilla Donut")
DonutShoppingCartDao-> delete method -> donut: Vanilla Donut
CassandraDonutDatabase-> delete
method -> donut: Vanilla Donut
res88: Boolean = true

scala> donutShoppingCart.checkStockQuantity("Vanilla Donut")
DonutInventoryService-> checkStockQuantity method -> donut: Vanilla Donut
CassandraDonutDatabase-> query method -> donut: Vanilla Donut
res89: Int = 1
scala>