CODEWITHSUNDEEP
scala
davetron5000
davetron5000

Reputation: 24821

Scala equivalent of Ruby's map.each?

Very handy Ruby code:

some_map.each do |key,value|
  # do something with key or value
end

Scala equivalent:

someMap.foreach( entry => {
  val (key,value) = entry
  // do something with key or value
})

Having to add the extra val line bugs me. I couldn't figure out how to state the function arg to extract the tuple, so I'm wondering is there a way to do this, or why is there no foreach that extracts the key and value for me?

Upvotes: 11

Views: 1401

Answers (4)

Viktor Klang
Viktor Klang

Reputation: 26579

I like this one:

scala> val foo = Map( 1 -> "goo", 2 -> "boo" )
foo: scala.collection.immutable.Map[Int,java.lang.String] = Map(1 -> goo, 2 -> boo)

scala> for ((k,v) <- foo) println(k + " " + v)
1 goo
2 boo

Upvotes: 11

Thomas Jung
Thomas Jung

Reputation: 33092

Function.tupled converts a function (a1, a2) => b) to a function ((a1, a2)) => b.

import Function._
someMap foreach tupled((key, value) => printf("%s ==> %s\n", key, value))

Upvotes: 2

andri
andri

Reputation: 11292

You don't need even the val in for loop:

Following ViktorKlang's example:

scala> val foo = Map( 1 -> "goo", 2 -> "boo" )
foo: scala.collection.immutable.Map[Int,java.lang.String] = Map(1 -> goo, 2 -> boo)

scala> for ((k, v) <- foo) println(k + " " + v)
1 goo
2 boo

Note that for is rather powerful in Scala, so you can also use it for sequence comprehensions:

scala> val bar = for (val (k, v) <- foo) yield k
bar: Iterable[Int] = ArrayBuffer(1, 2)

Upvotes: 5

sepp2k
sepp2k

Reputation: 370102

This works, too:

someMap.foreach {case (key, value) =>
  // do something with key and/or value
}

Upvotes: 19

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