Equivalent to Ruby's #tap method in Scala [dup

问题:

This question already has answers here:

how to keep return value when logging in scala (6 answers)

Closed 6 years ago.

Ruby has a method that allows us to observe a pipeline of values, without modifying the underlying value:

# Ruby
list.tap{|o| p o}.map{|o| 2*o}.tap{|o| p o}

Is there such a method in Scala? I believe this is called a Kestrel Combinator, but can't be sure.

回答1:

Here is one implementation on github: https://gist.github.com/akiellor/1308190

Reproducing here:

import collection.mutable.MutableList
import Tap._

class Tap[A](any: A) {
  def tap(f: (A) => Unit): A = {
    f(any)
    any
  }
}

object Tap {
  implicit def tap[A](toTap: A): Tap[A] = new Tap(toTap)
}

MutableList[String]().tap({m:MutableList[String] =>
  m += "Blah"
})

MutableList[String]().tap(_ += "Blah")

MutableList[String]().tap({ l =>
  l += "Blah"
  l += "Blah"
})