Table of Contents

Introduction

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 git@github.com: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

lukaszlenart/scala-basics

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