Option 包装一个值是一个好的模式吗? [英] Is Option wrapping a value a good pattern?

问题描述

我最近编写了以下 Scala 代码:

I recently wrote the following bit of Scala:

val f: File = ... // pretend this file came from somewhere
val foo = toFoo(io.Source.fromFile(f).mkString)

我真的不喜欢这种流动的方式.要了解发生了什么，您必须从中间的 f 开始，向左阅读 fromFile，向右阅读 mkString，再次向左阅读toFoo.呃.

I really didn't like the way this flowed. To understand what's happening, you have to start with f in the middle, read left to fromFile, read right to mkString, read left again to toFoo. Ugh.

特别是在习惯了序列的函数转换之后，这很难阅读.我的下一次尝试如下所示:

Especially after getting used to functional transformations of sequences, this is difficult to read. My next attempt looks like this:

val foo = Some(f)
  .map(io.Source.fromFile)
  .map(_.mkString)
  .map(toFoo)
  .get

我更喜欢这个流程.您可以看到发生了什么 这是对 Option 类的一个很好的使用吗?还是我滥用了?有没有更好的模式可以用来实现相同的流程?

I like the flow of this much better. You can see what happens Is this a good use of the Option class? Or am I abusing it? Is there a better pattern that I can use to achieve the same flow?

推荐答案

这完全没问题.但是，Scalaz 中有一种方法 |> 做得更好，如果您不想要所有 Scalaz，也可以自己创建:

This is perfectly okay. However, there is a method |> in Scalaz that does one better, and you can create it yourself if you don't want all of Scalaz:

class Piper[A](a: A) { def |>[B](f: A => B) = f(a) }
implicit def pipe_everything[A](a: A) = new Piper(a)

f |> io.Source.fromFile |> {_.mkString} |> toFoo

就我个人而言，我倾向于编写大量需要括号的代码，并且在大多数情况下我更喜欢方法而不是运算符，因此在我的代码中我通常称 |> use"，但它同样的交易:

Personally, I tend to write a lot of code that requires parentheses and I like methods better than operators in most cases, so in my code I normally call |> "use", but it's the same deal:

f.use(io.Source.fromFile).use(_.mkString).use(toFoo)

<小时>

在 Scala 2.11 或更高版本中，您可以使用(稍微)更少的语法获得相同的行为和改进的性能:

---

In Scala 2.11 or later, you can get the same behavior and improved performance with (slightly) less syntax:

implicit class Piper[A](private val a: A) extends AnyVal {
  def |>[B](f: A => B) = f(a)
}

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