如何在Kotlin中打印ClosedRange [英] How to print ClosedRange in Kotlin

问题描述

我正在学习Kotlin，并且试图不理解Ranges

I'm learning Kotlin , and I'm trying to undetstand Ranges

我如下创建了String范围

val alpha = "A".."Z"

我要为我写的内容打印

for (item in alpha) println(item)

但是它给出了错误

错误:(13，18)Kotlin:For循环范围必须具有'iterator()'方法

Error:(13, 18) Kotlin: For-loop range must have an 'iterator()' method

任何人都可以帮忙，如何打印此范围?

Can anyone help, how to print this range?

推荐答案

好吧，默认情况下您无法使用String做到这一点，因为对于ClosedRange<String>没有iterator()，但是Char可以工作直接:

Well you can't do it with Strings by default, since there's no iterator() for ClosedRange<String>, but Chars will work directly:

val r = 'A'..'Z'
r.forEach(::println)

它将是CharRange类型，并提供所需的iterator().

It will be of type CharRange and provide the needed iterator().

要使非常特殊的示例与String一起使用，可以定义自己的扩展函数并将其委托给Iterator<Char>:

To make your very special example work with Strings, you could define your own extension function and delegate to a Iterator<Char>:

operator fun ClosedRange<String>.iterator(): Iterator<String> {
    val charIt = (start.toCharArray().first()..endInclusive.toCharArray().first()).iterator()

    return object : Iterator<String> {
        override fun hasNext() = charIt.hasNext()
        override fun next(): String = charIt.nextChar().toString()
    }
}

现在它可以按您的意愿工作了.但是请注意，对于大多数String范围的用例，这没有意义.

Now it works as you wished. But be aware that this does not make sense for most use cases with ranges of String.

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