Kotlin 解构(operator component1)

operator: 将一个函数标记为重载一个操作符或者实现一个约定。
示例：

class User(var age: Int, var name: String) {
    //按照参数个数，必须在component后面加上1234
    operator fun component1() = age
    operator fun component2() = name
}

fun user2(){
        val user = User(18, "jack")
        //允许将user直接赋值给一个拆解后的对象(age和name)
        val (age, name) = user
        println("$age $name")
        //该解构方法应用于map的遍历比较方便
//        val map = mapOf("..key.." to "key","..value.." to "value")
        val map2 = mapOf(Pair("key..","value.."))
        //map可以直接解构
        for ((k,v) in map2){
            println("$k $v") //输出：key.. value..
        }
       //list的话需要用上withIndex，withIndex提供了一个迭代器
        val list = arrayListOf("a","b","c","d")
        for ((index,str) in list.withIndex()){
            println("第$index 个元素是$str")
        }
    }