kotlin半生对象

伴侣对象 (Companion object)

• If you need a function or a property to be tied to a class rather than to instances of it (similar to static in java), you can declare it inside a companion object:

  如果需要将函数或属性绑定到类而不是实例(类似于java中的static)，则可以在同伴对象中声明它：

• You can omit the name, in which case the name defaults to Companion,

  您可以省略名称，在这种情况下，名称默认为Companion，

  companion object 
        
         {    //Companion Object Body}
        

• Companion objects members can only be accessed via the containing class name, not via instances of the class.

  伴侣对象成员只能通过包含的类名称访问，而不能通过类的实例访问。

• A class has only one companion object.

  一个类只有一个伴随对象。

• Companion object initializes when class is loaded, (typically when first time reference from other code).

  伴侣对象在加载类时初始化(通常是在第一次从其他代码引用时)。

• Companion object has its own init block.

  伴随对象具有其自己的init块。

• The companion object is a singleton.

  伴随对象是单例。

Kotlin中的伴随对象特征程序 (Program for companion object features in Kotlin)

package com.includehelp//Declare classclass Car{    //class init block    init {        println("Init Block of Class")    }    //Make companion object    companion object {        //companion object init block        init {            println("Init Block of Companion object")        }        //property of companion object        val name="Tata Altroz !! "        //function in companion object        fun printName(){            println("Your Car name : $name")        }    }}//Main Function, Entry Point of Programfun main(){    //Call method with Class name,     //without create Instance of class,     //like static method in java    Car.printName()    //access Property using class name    val nameLen = Car.name.length    println("Car Name Length : $nameLen")}

Output:

输出：

Init Block of Companion objectYour Car name : Tata Altroz !! Car Name Length : 15

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kotlin半生对象