Kotlin 解构超过五个组件

发布于04月28日

我有一个正则表达式的结果，它将七个捕获组返回到一个数组中.

我以为我会使用解构，而不是使用数组元素的下标来构造我的对象，问题是我似乎只能有五个组件.

A minimal example:

//  val (a, b, c, d, e) = listOf(1, 2, 3, 4, 5)
val (a, b, c, d, e, f, g) = listOf(1, 2, 3, 4, 5, 6, 7)

Compiler output:

> Error:(70, 41) Kotlin: Destructuring declaration initializer of type
> List<Int> must have a 'component6()' function 
> Error:(70, 41) Kotlin: Destructuring declaration initializer of type 
> List<Int> must have a 'component7()' function

有没有办法拥有五个以上的组件，或者这是最大值？

推荐答案

List接口只定义了5个组件函数(作为扩展函数).

You can add your own component functions as extension functions:

operator fun <T> List<T>.component6() = this[5]
operator fun <T> List<T>.component7() = this[6]
// ...

This would work now:

val (a, b, c, d, e, f, g) = listOf(1, 2, 3, 4, 5, 6, 7)

从docs人中:

当然，也可以有component3()和component4()等等.

Note that the componentN() functions need to be marked with the operator keyword to allow using them in a destructuring declaration.