Kotlin解构whenif语句

发布于03月13日

所以我有一个字符串，我想判断我是否应该一分为二，或者返回一些默认值.如下所示:

val myString = "firstPart-secondPart"
val (first, second) = when (myString.contains("-")) {
        true -> myString.split('-', limit = 2)
        else -> ?? <-- How would i return ("Default1", "Default2") so the destructuring still works?
}

So my question is, how do i return two default strings, so that the deconstructing works? I've used String.split() before in order to deconstruct and it's really nice.

How to return 2 values for destructuring

You need to return a type matching the above type, split returns a list, so you could use this:

listOf("Default1", "Default2")

Full code

val myString = "firstPart-secondPart"
val (first, second) = when (myString.contains("-")) {
        true -> myString.split('-', limit = 2)
        else -> listOf("Default1", "Default2")
}

Why this works

由于两个分支都返回List<String>，所以可以将整个when块视为List<String>，因此可以对其进行分解以从中获取值.

Possible cleanup

val myString = "firstPart-secondPart"
val (first, second) = when {
    myString.contains("-") -> myString.split('-', limit = 2)
    else -> listOf("Default1", "Default2")
}

假设您要添加更多条件，这可能更有意义，否则IF可能更有意义.