Constuctors

 

// File:            Main.kt
// Programmer:      Engineer Nolverto Urias Obeso
// Creation Date:   06/17/2023
// Email:           nolvertou@gmail.com
// Description:     Learning how to use constructors and init
package Aquarium

fun main() {
    buildAquarium()

    fishExample()
}

fun buildAquarium() {

    val myAquarium = Aquarium()

    println("Length: ${myAquarium.length} cm, " +
            "Width: ${myAquarium.width} cm, " +
            "Height: ${myAquarium.height} cm")

    myAquarium.height = 80

    println("Height: ${myAquarium.height} cm")
    println("Volume: ${myAquarium.height} liters")

    val smallAquarium = Aquarium(length = 20, width = 15, height = 30)
    println("Small Aquarium: ${smallAquarium.volume} liters with " +
            "Length: ${smallAquarium.length} cm, " +
            "Width: ${smallAquarium.width} cm, " +
            "Height: ${smallAquarium.height} cm" )

    val smallAquarium2 = Aquarium(numberOfFish = 9)
    println("Small Aquarium 2: ${smallAquarium2.volume} liters with " +
            "Length: ${smallAquarium2.length} cm, " +
            "Width: ${smallAquarium2.width} cm, " +
            "Height: ${smallAquarium2.height} cm")

}


fun fishExample(){
    val fish = Fish(true, 20)
    println("Is the fish friendly? ${fish.friendly}. It needs volume ${fish.size}")
}

package Aquarium

// Most of the classes only provide a primary constructor
class Aquarium(var length: Int = 100, var width: Int = 20, var height: Int = 40) { // Primary Constructor
    var volume: Int
        get() = width * height * length / 1000   // It calculates the volume
        set(value){ height = (value * 1000) / (width * length)} // It sets the height giving the volume value

    var water = volume * 0.9    // It's used the 90% of the tank volume


    // The arguments have to match exactly the with one of the available constructors
    // If you declare a secondary constructor it must containt a call to the primary constructor by using this()
    constructor(numberOfFish:Int): this(){ // Secondary constructor
        val water:Int = numberOfFish * 2000 //cm3
        val tank: Double = water + water * 0.1
        height = (tank/(length*width)).toInt()  // Calculates the height depending of number of fish
    }

}

package Aquarium

class Fish(val friendly: Boolean = true, volumeNeeded : Int) {
    val size: Int

    // Note:    You can have more than 1 init{} block, and they always run before secondary constructors
    //          Init can be almost anywhere in your class
    //          They are executed in order, from the top of the class to the bottom
    //          So, if you were using any properties they need to come before the init blocks

    init{
        println("first init block")
    }

    // Calculate the size of that object creation time
    // Init works just like a constructor
    init {
        if(friendly){
            size = volumeNeeded
        }else{ // fish is aggressive
            size = volumeNeeded * 2
        }
    }

    init {
        println("constructed fish of size $volumeNeeded final size ${this.size}")
    }

    init{
        println("last init block")
    }

    // To write clean kotlin code just use one primary constructor and init blocks
    // When you need more flexibility consider adding helper functions like make default fish
    constructor(): this(true, 9){
        println("running secondary constructor")
    }
}