Table of Contents

• Introduction
  • Prerequisites
  • Scala basics
    • task:
  • SBT setting up project & basic commands
    • task1:
    • task2 (optional, do it at home):
  • Unit testing
    • task:
  • module1 - OOP
    • task1:
    • task2:
    • task3:
    • task4:
    • task5:
  • module2 - methods
    • task1:
    • task2:
  • module3 - collections & functional programming
    • task1:
    • task2:
    • task3:
    • task4:
  • module4 - Optionals & for-expressions
    • task1:
    • task2:
    • task3:
    • task4:
  • module5 - traits & inheritance
    • task1:
    • task2:
    • task3:
  • module6 - pattern matching
    • task1:
    • task2:
    • task3:
  • module7 - Higher Order Functions
    • task1:
    • task2:

Introduction

This is a basic Scala workshop to allow smooth introduction into principal Scala features.

Prerequisites

• install JDK8

• install sbt

• install IDE of your choice which supports Scala (IDEA Community Edition with Scala plugin is preferred)

• checkout the project

  git clone [email protected]:lukaszlenart/scala-basics.git

• start sbt within the project’s folder to download all the dependencies

Scala basics

• REPL, IntelliJ IDEA Scratch files

• val, var, def

• if, for

• String, Int

• generics

task:

• use REPL to sum two Ints and if the result is greater than 0 print it, in other case print a message

• use REPL to define a mutable empty String variable, then assign a message to the variable and if length of the message is greater than 10, print it 10 times, in other case just once

SBT setting up project & basic commands

• directory structure

• configuration files

• commands: compile, clean, reload, console, test, testOnly

task1:

• create a folder for a new project

• create src/main/resources, src/main/scala folders

• create src/test/resources, src/test/scala folders

• create build.sbt file in the root folder and define project’s basic information like name, version, scalaVersion and a first dependency

• start sbt in the root folder

task2 (optional, do it at home):

• use sbt new to generate a new project, use an example template from the page below

https://www.scala-sbt.org/1.0/docs/sbt-new-and-Templates.html

Unit testing

• ScalaTest, Spec2

• how to create a unit test

task:

• create a simple unit test with passing assertion

• create another simple unit test with failing assertion

• use test or testOnly to check results

• ignore the failing test and re-run the test

module1 - OOP

• class, case class

  • please do task1 and task2

• performing operations in constructor

  • please do task3

• object

• companion object & apply

  • please do task4 and task5

task1:

• create a class SimplePerson with String fields firstName and lastName

• define a method to calculate fullName - concatenate firstName and lastName

• create a unit test to cover the above logic

task2:

• repeat the same from task1 but using case class and class name Person

• add additional assertion to check if firstName and lastName have proper values

task3:

• create a case class AutoPerson with String fields firstName and lastName

• define a mutable String field fullName

• calculate the fullName in constructor

• create a unit test to cover the above logic

task4:

• create an object PersonSingleton

• define a mutable field fullName

• create two unit tests

• in the first one assign value to fullName and assert its value

• with the second test, assert only the value from the first test

task5:

• create a companion object for the case class Person

• define a method apply which accept just a single string

  • split the argument on white space to create a proper Person object

• create a unit test to cover creating a person based on a single string

module2 - methods

• default arguments

• named arguments

task1:

• create a case class Car with a field make: String

• define a method with at least two arguments

  • define the last argument with default value

• combine all the arguments and make field as a result

• create a unit test to cover calling the method using default value and passing specific value for the default argument

task2:

• create a case class Driver with at least two arguments:

  • licenseId

  • age

• define a method canDrive_? : Boolean to check if driver’s age is over or equal 18

• create a unit test to cover the method

• add additional assertion and use .copy() with named parameter to define a new value for the age

  • use assertion to check if the new value was properly re-defined

module3 - collections & functional programming

• Seq, List, Map, tuples

• elem :: Nil, head :: tail

  • please do task1 and task2

• .empty, .filter, .map, .find, .count, .sortBy

• .get, .head, .headOption

  • please do task3 and task4

task1:

• create a case class CarMileage with a field mileage: Seq

• create a unit test and init CarMileage using Seq(…​)

• assert if mileage value is the same as sequence using elem :: Nil construction

• assert if a first element of mileage value is the same using head :: tail construction

task2:

• create a case class CarGarage with field cars: Map[String, Car]

• define a method to find a car by given model

• define a method to count all cars in the Garage matching given model

• create a unit test to cover the above logic

task3:

• extend the case class Car and add a broken: Boolean field with default value set to false

• define additional method in CarGarage to list cars which are broken

• create a unit test to cover the above logic

task4:

• extend method from task3 to sort cars by make

• create a unit test to cover the logic

module4 - Optionals & for-expressions

• Option & None & Some

  • please do task1 and task2

• .flatMap, .map, .flatten

• simple for, for-comprehension

  • please do task3 and task4

task1:

• extend the class Car and define an optional field driver of type Driver with a default value

• create a unit test to cover creating a Car with and without the driver

task2:

• extend CarGarage with a method readyCars which looks for cars with the driver field defined

• create a unit test to cover the logic

task3:

• extend CarGarage with method readyDrivers which looks for cars with driver field defined and returns those drivers

• create a unit test to cover the logic

task4:

• redefine readyDrivers to use for-comprehension

  • you can use readDrivers1 name to keep the old version

• use the same unit test as in task3 to check if everything is ok

module5 - traits & inheritance

• trait, extends, with

• case objects (better than enums)

task1:

• define a trait Professional with method professionalDriverLicense

• define a new case class ProfessionalDriver which extends SimplePerson and with Professional trait

• implement missing method

  • you can extend SimplePerson and add optional driver license field with default value use this value to implement professionalDriverLicense method

  • or

  • define a new field in ProfessionalDriver class and use it to implement the method

• create a unit test to cover logic of professionalDriverLicense

task2:

• change implementation of professionalDriverLicense in Professional trait and return missing by default

• define a new case class SimpleDriver which extends SimplePerson and with Professional trait

• create a unit test to cover logic of default implementation

task3:

• define sealed trait DriverType

• create related companion object

• inside the companion object add two case object`s `Normal and Professional implementing the trait

• extend Driver case class and add optional driverType field of type DriverType

• create a test case covering creating Driver objects with both values of DriverType

module6 - pattern matching

• match & case

• unapply

task1:

• add additional type to DriverType - Missing

• extend Driver case class and define driverLicense method which returns driver’s licenseId prefixed with given type

• if type isn’t defined return only licenseId

• create a test case to cover this logic

task2:

• change logic of driverLicense method from task1 and if driverType equals Missing or is None return licenseId

• add additional test case to cover this logic

task3:

• create a companion object for CarGarage case class

• add ready_?(car: Car): Boolean method to the companion object

• return true if car is not broken and its make is "mercedes" and driver’s `age is over 18

• create a test case to check the implementation

module7 - Higher Order Functions

• functions that accept functions `def func(calcFn: Double ⇒ Double): Double

• functions that produce functions def builder(input: Double): Double ⇒ Double

  https://docs.scala-lang.org/tour/higher-order-functions.html

task1:

• define an object with a function that will produce a function based on a `driver’s type and will accept the driver based on his age:

  • a Normal driver can drive if his age is equal or over 18

  • a Professional driver can drive if his age is equal or over 21

  • any other driver cannot drive

• create a test case to check the implementation

task2:

• define a sealed trait CarMake with two case objects VW and Ford (similar to DriverType from module 5)

• define a case class LuxuryCar with a CarMake field

• define a passCertification function which accepts a function CarMake ⇒ Boolean and use it

• create a test case to check the implementation

  • if VW it should pass the certification

  • if Ford it shouldn’t pass the certification