应该避免 x._1,x._2... 语法吗? [英] Should x._1,x._2... syntax be avoided?

问题描述

我刚开始接触 Scala.我发现自己经常使用元组变量.

I'm just starting out in Scala. I find myself using tuple variables a lot.

例如，这是我写的一些代码:

For example, here's some code I wrote:

/* Count each letter of a string and return in a list sorted by character
 * countLetter("test") = List(('e',1),('s',1),('t',2))
*/
def countLetters(s: String): List[(Char, Int)] = {
  val charsListMap = s.toList.groupBy((c:Char) => c)
  charsListMap.map(x => (x._1, x._2.length)).toList.sortBy(_._1)
}

Scala 开发人员不喜欢这种元组语法(x._1、x._2 等)吗?

Is this tuple syntax (x._1, x._2 etc) frowned upon by Scala developers?

推荐答案

Scala 开发人员是否不喜欢元组访问器?

Are the tuple accessors frowned upon by Scala developers?

简答:没有.

稍长(一个字符)答案:是的.

Slightly longer (by one character) answer: yes.

过多的 _n 可能是代码异味，在我看来，以下情况更清晰:

Too many _n's can be a code smell, and in your case the following is much clearer, in my opinion:

def countLetters(s: String): List[(Char, Int)] =
  s.groupBy(identity).mapValues(_.length).toList.sortBy(_._1)

有很多像 mapValues 这样的方法专门设计用于减少对嘈杂的元组访问器的需求，所以如果你发现自己在编写 _1 等，，很多，这可能意味着您缺少一些不错的库方法.但有时它们是最干净的写东西的方式(例如，我重写中的最终 _1).

There are lots of methods like mapValues that are specifically designed to cut down on the need for the noisy tuple accessors, so if you find yourself writing _1, etc., a lot, that probably means you're missing some nice library methods. But occasionally they're the cleanest way to write something (e.g., the final _1 in my rewrite).

另一件需要注意的事情是，过度使用元组访问器应该被视为将元组提升为案例类的推动力.考虑以下几点:

One other thing to note is that excessive use of tuple accessors should be treated as a nudge toward promoting your tuples to case classes. Consider the following:

val name = ("Travis", "Brown")

println("Hello, " + name._1)

相反:

case class Name(first: String, last: String)

val name = Name("Travis", "Brown")

println("Hello, " + name.first)

第二个版本中额外的案例类定义为一行代码带来了很多可读性.

The extra case class definition in the second version buys a lot of readability for a single line of code.

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