是否有类似Java Stream的“窥视"功能?在Scala中进行操作? [英] Is there something like Java Stream's "peek" operation in Scala?

问题描述

在Java中，您可以在Stream上调用peek(x -> println(x))，它将为每个元素执行操作并返回原始流，这与foreach不同，它是Unit. Scala中有类似的东西吗?理想情况下，它适用于所有Monady类型的东西，允许您在执行副作用操作时通过"原始Monad吗? (例如，正在记录)

In Java you can call peek(x -> println(x)) on a Stream and it will perform the action for each element and return the original stream, unlike foreach which is Unit. Is there something similar in Scala, ideally something which works on all Monady types, allowing you to "pass through" the original Monad while performing a side effect action? (Logging, e.g.)

它当然很容易实现:

def tap[A, U](a: A)(action: (A) => U): A = {
  action(a)
  a
}

但是我希望有一些更优雅或更惯用的东西.

but I'm hoping for something a bit more elegant or idiomatic.

推荐答案

一种解决方法是使用隐式:

One way to solve this is using implicits:

class Tappable[A](a: A) {
  def tap[U](action: (A) => U): A = {
    action(a)
    a
  }
}

implicit def any2Tappable[A](a: A): Tappable[A] = new Tappable[A](a)

然后可以将其本地使用:

Which can then be used natively:

connection.tap(_.connect()) match {
  case c if c.getResponseCode == 304 => None
  ...

还有其他答案吗?

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