kotlin 扩展类的功能_Kotlin程序| 扩展功能功能

朴灿烈づ我的快乐病毒、 2023-03-05 12:52 18阅读 0赞

kotlin 扩展类的功能

## 扩展功能 **(**Extension function**)** ##

*  Kotlin provides the ability to add more functionality to the existing class without inheriting them.
    
    Kotlin可以在不继承现有类的情况下为其添加更多功能。
 *  This is done via a special declaration called "Extension'.
    
    这通过称为“扩展”的特殊声明来完成。
 *  When a function added into an existing User-defined or Library class called '**Extension Function**'.
    
    当函数添加到现有的用户定义或库类中时，称为“ **扩展函数** ”。
 *  It can also define extensions of functions and properties for companion objects.
    
    它还可以定义伴随对象的功能和属性的扩展。

## Kotlin扩展功能功能程序 **(**Program for extension function features in Kotlin**)** ##

package com.includehelp
    
    // Declare class
    class MyClass1{
        // Member function
        fun sayHello(){
            println("Say Hello")
        }
    }
    
    // Declare class
    class MyClass2{
        // create companion object to call method with class name
        companion object{
            // companion object function
            fun display(){
                println("Display from Companion Object !!")
            }
        }
    }
    
    // define Extension function for MyClass1
    fun MyClass1.greetExtn(){
        println("Greetings from Extension Function !!")
    }
    
    // define extension for Int Class
    fun Int.isOdd(){
        if(this%2==0){
            println("Number is ODD")
        }
    }
    
    // Define Extension function for MyClass2 Companion object
    fun MyClass2.Companion.printData(){
        println("Extension function for Companion object !!")
    }
    
    // Main Function, Entry point of Program
    fun main(){
        // Create Instance
        val myClass1 = MyClass1()
    
        // Called member function of class
        myClass1.sayHello()
    
        // Called extension function
        myClass1.greetExtn()
    
        // Called Int Class extension Function
        24.isOdd()
    
        // Called companion object member function
        MyClass2.display()
    
        // Called companion object extension function
        MyClass2.printData()
    }

**Output:**

**输出：**

Say Hello
    Greetings from Extension Function !!
    Number is ODD
    Display from Companion Object !!
    Extension function for Companion object !!

> 翻译自: [https://www.includehelp.com/kotlin/extension-function-features.aspx][https_www.includehelp.com_kotlin_extension-function-features.aspx]

kotlin 扩展类的功能

[https_www.includehelp.com_kotlin_extension-function-features.aspx]: https://www.includehelp.com/kotlin/extension-function-features.aspx