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@rodobarcaaa
Last active October 31, 2023 16:20
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Scala Classes Examples
object Classes {
class MyFirstClass
val myFirstClass = new MyFirstClass
//---------------------------------------------//
class Vehicle(
var passengers: Int, //number of passengers
var speed: Int, //speed value
val unit: String //speed unit
) {
override def toString: String = s"(passengers: $passengers, speed: $speed $unit)"
}
val bicycle = new Vehicle(1, 30, "km")
bicycle.passengers // 1
bicycle.passengers = 2
bicycle.passengers // 2
println(bicycle) // (passengers: 2, speed: 30 km)
//---------------------------------------------//
class Vehicle1(
var passengers: Int,
private val speed: Int,
private val unit: String = "km"
) {
val speedDescription: String = s"$speed $unit"
override def toString: String = s"(passengers: $passengers, speed: $speedDescription)"
}
object Vehicle1 {
def speed220km(passengers: Int): Vehicle1 = new Vehicle1(passengers, 220, "km")
}
val motorcycle = new Vehicle1(2, 100)
motorcycle.passengers // 2
motorcycle.speed // don't compile because the attribute is private
motorcycle.speedDescription // 100 km
println(motorcycle) // (passengers: 2, speed: 100 km)
val car: Vehicle1 = Vehicle1.speed220km(5)
println(car) // (passengers: 5, speed: 220 km)
//---------------------------------------------//
case class Vehicle2(passengers: Int, speed: Int, unit: String) {
val speedDescription: String = s"$speed $unit"
}
// Normal constructor and the most used
val myCar = Vehicle2(5, 200, "km")
// Using apply explicitly
val myCar1 = Vehicle2.apply(5, 200, "km")
// By "tuple" of values
val myCar2 = Vehicle2.tupled((5, 200, "km"))
// Through currying mode parameters
val myCar3 = Vehicle2.curried(5)(200)("km")
// use the automatically generated methods
myCar.passengers // 5
myCar.speed // 200
myCar.speed = 300 // don't compile -> error: reassignment to val
myCar.unit // km
println(myCar) // Vehicle2(5,200,km)
val myFastCar = myCar.copy(passengers = 2, speed = 320)
println(myFastCar) // Vehicle2(2,320,km)
// compare by structure and not by reference
myCar == myCar1 // true
myCar == myCar2 // true
myCar == myCar3 // true
myCar == myFastCar // false
// use the unapply in match expressions
def recognizeVehicle(x: Vehicle2): String = x match {
case Vehicle2(10, speed, unit) =>
s"10 passenger minivan with speed of $speed $unit"
case Vehicle2(2, speed, _) if speed > 300 =>
s"High speed sports car ${x.speedDescription}"
case _ =>
"Any non-minivan or sports car: " + x
}
val minivan = Vehicle2(10, 100, "km")
println(recognizeVehicle(minivan))
// 10 passenger minivan with speed of 100 km
println(recognizeVehicle(myFastCar))
// High speed sports car 320 km
println(recognizeVehicle(myCar))
// Any non-minivan or sports car: Vehicle2(5,200,km)
//--------------------------------------------------//
sealed trait Animal {
def name: String
}
case class Dog(name: String, owner: String) extends Animal
case class Cat(name: String, color: String) extends Animal
def recognizeAnimal(a: Animal): String = a match {
case Dog(name, owner) => s"The dog $name belongs to $owner."
case Cat(name, color) => s"${name.capitalize} is a very beautiful $color cat."
}
val bony = Dog("Bony", "Pedrito")
val tom = Cat("tom", "negro")
println(recognizeAnimal(bony))
// The dog Bony belongs to Pedrito.
println(recognizeAnimal(tom))
// Tom is a very beautiful black cat.
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