MoraSoftware.github.io/class.html at master · MoraSoftware/MoraSoftware.github.io · GitHub

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<!DOCTYPE html>
<html lang="en">
   <head>
      <title>Class Kotlin</title>
      <meta charset="utf-8">
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      <meta name="theme-color" content="#111111">
      <meta name="og:type" content="website">
      <meta name="og:title" content="MoraSoftware.github.io">
      <meta name="og:description" content="Mora Software">
      <meta name="og:site_name" content="Mora Software">
      <meta name="og:url" content="{{ site.url }}">
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   </head>
   <body>
      <div class="container">
         <div class="block">
            <form action="index.html">
               <input type="image" src="static/white.jpg" />
            </form>
         </div>
         <div class="block">
            <h2>Functions Kotlin</h2>
         </div>
         <ul class="nav nav-tabs">
            <li class="active"><a data-toggle="tab" href="#init">Init</a></li>
            <li><a data-toggle="tab" href="#inheritance">Inheritance</a></li>
            <li><a data-toggle="tab" href="#override">Override</a></li>
            <li><a data-toggle="tab" href="#InheritanceSecondary">Inheritance Secondary Constructors</a></li>
            <li><a data-toggle="tab" href="#visibility">Visibility</a></li>
            <li><a data-toggle="tab" href="#abstract">Abstract</a></li>
            <li><a data-toggle="tab" href="#interface">Interface</a></li>
            <li><a data-toggle="tab" href="#data">Data Clases</a></li>
            <li><a data-toggle="tab" href="#sealed">Sealed</a></li>
         </ul>
         <div class="tab-content">
            <div id="init" class="tab-pane fade in active">
               <h3>Class, Primary Constructor, Secondary Constructor and Init Block</h3>
               <xmp>
                  fun main(args: Array<String>) {

                    var student = Student("Steve", 10)

                    println(student.id)
                  }

                  class Student(var name: String) {

                    var id: Int = -1

                    init {
                      println("Student has got a name as $name and id is $id")
                    }

                    constructor(n: String, id: Int): this(n) {
                      // The body of the secondary constructor is called after init block
                      this.id = id
                    }
                  }
               </xmp>
            </div>
            <div id="inheritance" class="tab-pane fade">
               <h3>Inheritance</h3>
               <xmp>
                fun main(args: Array<String>) {

                  var dog = Dog()
                  dog.bread = "labra"
                  dog.color = "black"
                  dog.bark()
                  dog.eat()

                  var cat = Cat()
                  cat.age = 7
                  cat.color = "brown"
                  cat.meow()
                  cat.eat()

                  var animal = Animal()
                  animal.color = "white"
                  animal.eat()
                }

                open class Animal {         // Super class / Parent class /  Base class

                  var color: String = ""

                  fun eat() {
                    println("Eat")
                  }
                }

                class Dog : Animal() {      // Sub class / Child class / Derived class

                  var bread: String = ""

                  fun bark() {
                    println("Bark")
                  }
                }

                class Cat : Animal() {      // Sub class / Child class / Derived class

                  var age: Int = -1

                  fun meow() {
                    println("Meow")
                  }
                }
               </xmp>
               <hr>
               <p>by default Class are:</p>
               <p>*public</p>
               <p>*final</p>
               <p>So for inheritance you need to make a class --OPEN--</p>
            </div>
            <div id="override" class="tab-pane fade">
               <h3>Override</h3>
               <xmp>
                fun main(args: Array<String>) {

                  var dog = MyDog()

                  println(dog.color)

                  dog.eat()
                }

                open class MyAnimal {

                  open var color: String = "White"

                  open fun eat() {
                    println("Animal Eating")
                  }
                }

                class MyDog : MyAnimal() {

                  var bread: String = ""

                  override var color: String = "Black"

                  fun bark() {
                    println("Bark")
                  }

                  override fun eat() {
                    super<MyAnimal>.eat()
                    println("Dog is eating")
                  }
                }
               </xmp>
               <hr>
               <p>Overriding Member Functions and variable</p>
               <p>Just like Kotlin classes, members of a Kotlin class are also public and final by default.
               <p>To allow a member function to be overridden, you need to mark it with the open modifier.</p>
               <p>Moreover, The derived class that overrides a base class function must use the override modifier, otherwise, the compiler will generate an error</p>
            </div>
            <div id="InheritanceSecondary" class="tab-pane fade">
               <h3>Inheritance with Primary and Secondary Constructors</h3>
               <xmp>
                fun main(args: Array<String>) {

                  var dog = TheDog("Black", "Pug")
                }

                open class TheAnimal {      // Super class / Parent class /  Base class

                  var color: String = ""

                  constructor(color: String) {
                    this.color = color
                    println("From Animal: $color")
                  }
                }

                class TheDog : TheAnimal {    // Sub class / Child class / Derived class

                  var bread: String = ""

                  constructor(color: String, breed: String): super(color) {
                    this.bread = breed

                    println("From Dog: $color and $breed")
                  }
                }
               </xmp>
               <hr>
               <p>Inheritance with Primary and Secondary Constructors</p>
            </div>
            <div id="visibility" class="tab-pane fade">
               <h3>Visibility Modifiers</h3>
               <xmp>

               open class Person { // Super class
                private val a = 1
                protected val b = 2
                internal val c = 3
                val a = 10
               }

               class Indian: Person() { // Sub class


                fun printTest() {
                  print(a)

                  // a is not visible
                  // b, c, d are visible
                }
               }

               class TestClass {
                fun testing() {
                  var person = Person()
                  print(person.a)
                  // a, b are not visible
                  // c, d are visible
                }
               }
               </xmp>
               <hr>
               <p>public always is visible</p>
               <p>protected visible inside sub class, not visible inside other class</p>
               <p>internal visible from module</p>
               <p>private just visible from yourClass.kt</p>
            </div>
            <div id="abstract" class="tab-pane fade">
               <h3>Abstract Class</h3>
               <xmp>
                fun main(args: Array<String>) {

                  //    var person = MyPerson()   // Not allowed. You cannot create instance of abstract class

                 var person = Indian()       // Allowed. Abstract Super class reference variable
                                // pointing to child class object.
                 person.name = "Steve"
                 person.eat()
                 person.goToSchool()
                }

                abstract class MyPerson {     // you cannot create instance of abstract class

                  abstract var name: String

                  abstract fun eat()      // abstract properties are 'open' by default

                  open fun getHeight() {} // A 'open' function ready to be overridden

                  fun goToSchool() {}     // A normal function
                }

                class Indian: MyPerson() {

                  override var name: String = "dummy_indian_name"

                  override fun eat() {
                    // Our own code
                  }
                }
               </xmp>
               <hr>
               <p>The Role or Abstract class is to just provide set of methods and properties</p>
               <p>Abstract Class are Partlally  defined class</p>
               <p>Abstract Methods have no body when declared</p>
               <p>Abstract Property cannot be initialized when declared</p>
               <p>CONCLUSION</p>
               <p>you cannot create intance/objects of ABSTRACT class</p>
               <p>you need to override ABSTRACT methods, propertics inside Derived class</p>
            </div>
            <div id="interface" class="tab-pane fade">
               <h3>Interface</h3>
               <xmp>
                fun main(args: Array<String>) {

                  var myButton = MyButton()
                  myButton.onTouch()
                  myButton.onClick()
                }

                interface MyInterfaceListener {     // You cannot create the instance of interface

                  fun onTouch()                   // Methods in interface are abstract by default

                  fun onClick() {                 // Normal methods are public and open by default but NOT FINAL
                    println("MyInterfaceListener: onClick")
                  }
                }

                interface MySecondInterface {       // You cannot create the instance of interface

                  fun onTouch() {                 // Normal Method
                    println("MySecondInterface: onTouch")
                  }

                  fun onClick() {                 // Normal methods are public and open by default but NOT FINAL
                    println("MySecondInterface: onClick")
                  }

                }

                class MyButton: MyInterfaceListener, MySecondInterface {

                  override fun onTouch() {
                    super<MyInterfaceListener>.onClick()
                    super<MySecondInterface>.onClick()
                  }

                  override fun onClick() {
                    super.onTouch()
                  }
                }
               </xmp>
               <hr>
               <p>Interface can contains both NORMAL methods and ABSTRACT methods</p>
               <p>But they contain only ABSTRACT PROPERTY</p>
               <p>Interface is not class</p>
               <p>You can not  create instance of an INTERFACE</p>
               <p>similar to an ABSTRACT class</p>
            </div>
            <div id="data" class="tab-pane fade">
               <h3>Data Clases</h3>
               <xmp>
               fun main(args: Array<String>) {

                var user1 = User("Sam", 10)

                var user2 = User("Sam", 10)

                println(user1.toString())

                if (user1 == user2)
                  println("Equal")
                else
                  println("Not equal")

                var newUser = user1.copy(id = 25)
                println(newUser)
              }

              data class User(var name: String, var id: Int)
               </xmp>
               <hr>
               <p>Any class contains functions such as:</p>
               <p>equals():Boolean</p>
               <p>hasCode():Int</p>
               <p>toString:String</p>
               <p>------------------</p>
               <p>Kotlin creates a copy() too</p>
            </div>
            <div id="sealed" class="tab-pane fade">
               <h3>Sealed</h3>
               <xmp>
                sealed class Expr
                data class Const(val number: Double) : Expr()
                data class Sum(val e1: Expr, val e2: Expr) : Expr()
                object NotANumber : Expr()

                fun eval(expr: Expr): Double = when(expr) {

                  is Const -> expr.number
                  is Sum -> eval(expr.e1) + eval(expr.e2)
                  NotANumber -> Double.NaN
                  // the `else` clause is not required because we've covered all the cases
                }
               </xmp>
               <hr>
               <p>Sealed classes are used for representing restricted class hierarchies</p>
               <p>when a value can have one of the types from a limited set, but cannot have any other type</p>
               <p></p>
               <p>They are, in a sense, an extension of enum classes:</p>
               <p>- the set of values for an enum type is also restricted,</p>
               <p>- but each enum constant exists only as a single instance</p>
               <p>- whereas a subclass of a sealed class can have multiple instances which can contain state</p>
               <a href="https://www.youtube.com/watch?v=P2ds5vTFIOw"><img src="static/youtube.png"></a>
               <p></p>
            </div>
         </div>
      </div>
   </body>
</html>