name: portada
class: portada-slide, center, middle

# Kotlin
## Poo

<%= teacher_slides_start %>

---
# Classe

```kotlin
class Car(val model:String, val price: Double? = null)
```

---
# Atributs

```kotlin
// Atributs definits a la constructora (var o val)
class Rectangle(var height:Double, var width:Double){
    // Més atributs
    val createdAt = Instant.now()

// Atribut calculats
    val area get() = height * width
}

fun main(){
    val rectangle = Rectangle(2.0,4.0)
    //Accés als atributs
    println(rectangle.width)
    println(rectangle.createdAt)
    println(rectangle.area)
}
```

---
# Init
```kotlin
class Sample1(val attribute1: Int, notAnAttribute: Int){
    val attribute2 : Int
    init {
    attribute2 = notAnAttribute
    }
}
```

```
val sample = Sample1(1,2)
println(sample.attribute1)
// println(sample.notAnAttribute) <- Invalid
println(sample.attribute2)
```
---
# Init
```
class Size(width: Int, height: Int) {
  init {
      // assert assegura que es complexi la condició,
      // sinó llança una excepció
      assert(width < 0) {"Width can't be negative"}
      assert(height < 0) {"height can't be negative"}
  }
}
```

---
# Constructors secundari

```kotlin
data class Car(
    val model: String,
    val price: Double? = null,
    val old: Boolean
){
    constructor(
        model: String,
        price: Double? = null,
        year: Int
    ) : this(model, price, year<2000)
}
```

---
# Visibilitat
- For members declared inside a class:
    - __private__ El membres són visibles només en aquesta classe.
    - __protected__ Els membres són visibles per aquesta classe i subclasses.
    - __internal__ Els membres són visibles des de dins del mòdul.
    - __public__ els membres són accessibles des de fora de la classe.

---
# Visibilitat

```
class SomeClass {
    private val privateVal = 1
    protected val protectedVal = 2
    internal val internalVal = 3
    val publicVal = 4  // public by default

protected fun privateMethod() {}
    fun publicMethod() {} // public by default
}

fun main() {
    val instance = SomeClass()
//  instance.privateVal  <- No visible
//  instance.protectedVal  <- No visible
    instance.publicVal
    instance.internalVal
//  instance.privateMethod() <- No visible
    instance.publicMethod()
}
```

---
# Default and named arguments
```
class Size(var width: Int = 1, var height: Int = 1) {
    val area get() = height * width
}
```

```
val size1 = Size(3, 5) // width == 3, height == 5
val size2 = Size(width = 3, height = 5) // width == 3, height == 5
val size3 = Size(height = 5, width = 3) // width == 3, height == 5
val sizeWide = Size(10) // width == 10, height == 1 poc llegible!
val sizeHigh = Size(height = 10) // width == 1, height == 10
```

---
# Enum

```kotlin
enum class DayOfWeek {
    SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
}

```

```kotlin
val dow = DayOfWeek.MONDAY
```

---
# Enum

```kotlin
fun tellItLikeItIs() = when (dow) {
    MONDAY -> "Mondays are bad."
    TUESDAY, WEDNESDAY, THURSDAY -> "Midweek days are so-so."
    FRIDAY -> "Fridays are better."
    SATURDAY, SUNDAY -> "Weekends are best."
}
```
---

Enumeracions: https://fp.mateuyabar.com/DAM-M03/UF4/02_enums.html
Herència: https://fp.mateuyabar.com/DAM-M03/UF4/03_inheritance.html
Classes abstractes i interfícies: https://fp.mateuyabar.com/DAM-M03/UF4/04_classes_abstractes.html
Introducció a generics: https://fp.mateuyabar.com/DAM-M03/UF4/91_introduccio_a_generics.html
Delegate: https://fp.mateuyabar.com/DAM-M03/UF4/92_delegation.html

---
# Exercicis
- https://fp.mateuyabar.com/DAM-M03/UF4/exercicis/01_exercicis.html
  - exercicis: 2, 3, 4
- [mostpopulatedcountries](https://fp.mateuyabar.com/DAM-M03/UF1/exercicis/06_list.html#mostpopulatedcountries)