Classes and Objects

Object State

Use a value stored inside an object.

state Object state is data stored by an object and used by its methods.

Object State

points
ObjectState.kt
Replay: real traced execution (multi-file project)
class ScoreBox(var score: Int) {
    fun afterAdd(points: Int): Int {
        return score + points
    }
}

fun main() {
    val points = 4
    val box = ScoreBox(10)
    val finalScore = box.afterAdd(points)

    println("points=$points")
    println("score=$finalScore")
}

class ScoreBox(var score: Int) {
    fun afterAdd(points: Int): Int {
        return score + points
    }
}

fun main() {
    val points = 1
    val box = ScoreBox(10)
    val finalScore = box.afterAdd(points)

    println("points=$points")
    println("score=$finalScore")
}

class ScoreBox(var score: Int) {
    fun afterAdd(points: Int): Int {
        return score + points
    }
}

fun main() {
    val points = 6
    val box = ScoreBox(10)
    val finalScore = box.afterAdd(points)

    println("points=$points")
    println("score=$finalScore")
}

  1. points ← 4

    7fun main() {8    val points→ 4 = 4 //@points=1, 69    val box = ScoreBox(10)10    val finalScore = box.afterAdd(points4)

  2. fun afterAdd(points: Int): Int

    1class ScoreBox(var score: Int) {2    fun afterAdd(points4: Int): Int {3        return score10 + points44    }

  3. finalScore ← 14

    9    val box = ScoreBox(10)10    val finalScore→ 14 = box.afterAdd(points4)1112    println("points=$points4")13    println("score=$finalScore14")14}
    outputpoints=4
score=14

  1. points ← 1

    7fun main() {8    val points→ 1 = 19    val box = ScoreBox(10)10    val finalScore = box.afterAdd(points1)

  2. fun afterAdd(points: Int): Int

    1class ScoreBox(var score: Int) {2    fun afterAdd(points1: Int): Int {3        return score10 + points14    }

  3. finalScore ← 11

    9    val box = ScoreBox(10)10    val finalScore→ 11 = box.afterAdd(points1)1112    println("points=$points1")13    println("score=$finalScore11")14}
    outputpoints=1
score=11

  1. points ← 6

    7fun main() {8    val points→ 6 = 69    val box = ScoreBox(10)10    val finalScore = box.afterAdd(points6)

  2. fun afterAdd(points: Int): Int

    1class ScoreBox(var score: Int) {2    fun afterAdd(points6: Int): Int {3        return score10 + points64    }

  3. finalScore ← 16

    9    val box = ScoreBox(10)10    val finalScore→ 16 = box.afterAdd(points6)1112    println("points=$points6")13    println("score=$finalScore16")14}
    outputpoints=6
score=16