Kotlin’s Way of Advancement 5 class use

1. The nested class

---

/** * class can be nested in other classes ** /

/ / news
class News{
    // Default locale
    private var lang ="cn"

    // News classification: nested class, and the main class is not very close, just a form of cooperation
    class Category{
        var list = arrayOf("Recommended"."Video"."Hot spots"."Science and technology"."The beauty")

        val listDesc =list.joinToString()
    }
    // Inner class: news language, usually used for classes that are not directly external, main class service
    inner class Language{
        fun changeRegion(newRegion: String){
            // The inner class can access the attributes of the main class
            lang =newRegion
            println("You can check$newRegion"+ "Regional news")}}}fun main(args: Array<String>) {
    // Displays a list of news items in China
    println(News.Category().listDesc)

    // To change the news locale, the inner class must have an instance of the main class, plus its own instance, to use it
    News().Language().changeRegion("us")}Copy the code

---

Recommendations, videos, hot topics, technology, and beautiful women can check out US regional newsCopy the code

2. Data classes

---

/** * class can be nested in other classes ** /

/ / news
class News{
    // Default locale
    private var lang ="cn"

    // News classification: nested class, and the main class is not very close, just a form of cooperation
    class Category{
        var list = arrayOf("Recommended"."Video"."Hot spots"."Science and technology"."The beauty")

        val listDesc =list.joinToString()
    }
    // Inner class: news language, usually used for classes that are not directly external, main class service
    inner class Language{
        fun changeRegion(newRegion: String){
            // The inner class can access the attributes of the main class
            lang =newRegion
            println("You can check$newRegion"+ "Regional news")}}}fun main(args: Array<String>) {
    // Displays a list of news items in China
    println(News.Category().listDesc)

    // To change the news locale, the inner class must have an instance of the main class, plus its own instance, to use it
    News().Language().changeRegion("us")}Copy the code

---

Recommendations, videos, hot topics, technology, and beautiful women can check out US regional newsCopy the code

3. The enumeration class

---

/** * Enumeration classes: a finite number of types of enumeration *, each of which is called an enumeration constant (with an initial value), separated by commas */

// Card suit
enum class PokerCard{hearts, diamonds, clubs, spades}// Clothes size: enumeration class with constructor
enum class Size(val height:Int)
{
    S(150),M(160),L(170),XL(180),XXL(190)}fun main(args: Array<String>) {
    // Enumerates the constants of the enumerated class
    println(PokerCard.values().joinToString())

    // Enumerate constants
    println(Size.valueOf("XXL").name)
    // Enumerate constant sort
    println(Size.valueOf("XXL").ordinal)

    println(Size.values().joinToString { it.name +":"+it.height })
}
Copy the code

---

Hearts, diamonds, clubs, spades XXL4
S:150, M:160, L:170, XL:180, XXL:190
Copy the code