클래스, 객체와 패키징

Scala 객체 지향 프로그래밍 소개

클래스: 설계도

class Car {
  // Properties and methods go here
}

간단한 클래스 정의하기

class Dog {
  // This dog has no properties or behaviors yet
}

object Main {
  def main(args: Array[String]): Unit = {
    println("Dog class defined!")
  }
}

객체(인스턴스) 생성하기

class Dog {
  // Still an empty dog blueprint
}

object Main {
  def main(args: Array[String]): Unit = {
    val myDog = new Dog()
    val yourDog = new Dog()
    println("Two dog objects created!")
  }
}

클래스에 속성 추가하기

class Dog(val name: String, val breed: String) {
  // 'val' makes name and breed immutable properties
}

object Main {
  def main(args: Array[String]): Unit = {
    val myDog = new Dog("Buddy", "Golden Retriever")
    println(s"My dog's name is ${myDog.name} and breed is ${myDog.breed}.")
  }
}

동작(메서드) 추가하기

class Dog(val name: String, val breed: String) {
  def bark(): String = {
    s"${name} says Woof!"
  }
}

object Main {
  def main(args: Array[String]): Unit = {
    val myDog = new Dog("Max", "Labrador")
    println(myDog.bark())
  }
}

Scala의 `object`(싱글턴)

object MathUtils {
  def add(a: Int, b: Int): Int = a + b
  def subtract(a: Int, b: Int): Int = a - b
}

object Main {
  def main(args: Array[String]): Unit = {
    val sum = MathUtils.add(5, 3)
    println(s"5 + 3 = ${sum}")
  }
}

컴패니언 객체

class Circle(val radius: Double) {
  def area: Double = Circle.PI * radius * radius
}

object Circle {
  // This is the companion object for the Circle class
  val PI: Double = 3.14159
  def apply(r: Double): Circle = new Circle(r) // Factory method
}

object Main {
  def main(args: Array[String]): Unit = {
    val c = Circle(5.0) // Using the apply method from companion object
    println(s"Circle area: ${c.area}")
  }
}

패키지로 코드 구성하기

package com.coddykit.animals

class Cat(val name: String) {
  def meow(): String = s"${name} says Meow!"
}

// This class is now inside com.coddykit.animals package

패키지에서 멤버 가져오기

package com.coddykit.app

// Define a class in a package first for import example
package com.coddykit.animals {
  class Cat(val name: String) {
    def meow(): String = s"${name} says Meow!"
  }
}

import com.coddykit.animals.Cat

object Main {
  def main(args: Array[String]): Unit = {
    val myCat = new Cat("Whiskers")
    println(myCat.meow())
  }
}

빠른 확인: 클래스일까요, 객체일까요?

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