kotlin 構造函數

主要建設者 (Primary Constructor)

• A Kotlin class have Primary constructor and one or more Secondary constructor.

  Kotlin類具有Primary構造函數和一個或多個Secondary構造函數。

• In Kotlin, Primary Constructor is the Part of Class Header.

  在Kotlin中，主要構造函數是類標題的一部分。

• Syntax:

  句法：

  class <Class Name> constructor(<optional Parameters>){// Class Body }

• The default visibility of the constructor will be public.

  構造函數的默認可見性將是public。

• Parameter of the primary constructor can be used in property initializer, declared in the class body.

  可以在類體內聲明的屬性初始化程序中使用主構造函數的參數。

演示Kotlin中主要構造函數示例的程序 (Program to demonstrate the example of Primary Constructor in Kotlin)

// Declare Class, with Primary Constructor keyword, // with one Parameter class Dog constructor(name:String){// Used Constructor Parameter to initialize property// in class body// String? for nullable property, // so property also contain nullprivate var name:String?=namefun getDogName(): String?{return name} }/*A) Constructor Keyword can be omitted if constructor does not have annotations and visibility modifiers. */ // Declare class, omitted Constructor Keyword class Horse (name:String){// Used Constructor Parameter to // initialize property in class bodyprivate var name:String =name.toUpperCase()fun getHorseName(): String?{return name} }/*A) Kotlin has concise Syntax to declaring property and initialize them from primary constructor.class Employee(var empName:String, val salary:Int)B) same way as regular properties declaration, properties declare in primary constructor can be var (mutable) or val (immutable)*/// Declare class, Properties declare in primary constructor class Cat(private var name:String, private val age:Int){fun setCatName(name:String){this.name =name}fun printData(){println("Name : $name and Age : $age")} }// Main Function, entry Point of Program fun main(args:Array<String>){// Create Dog Class Objectval dog = Dog("tommy")println("Dog Name : ${dog.getDogName()}")// Create Horse Class objectval horse =Horse("Chetak")println("Horse Name : ${horse.getHorseName()}")// Create Cat Class objectval cat = Cat("Katrina",32)cat.printData()cat.setCatName("Micy")cat.printData() }

Output:

輸出：

Dog Name : tommy Horse Name : CHETAK Name : Katrina and Age : 32 Name : Micy and Age : 32

翻譯自: https://www.includehelp.com/kotlin/example-of-primary-constructor.aspx

kotlin 構造函數

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