Scala相当于Ruby的map.each？

Question

非常方便的Ruby代码:

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

Scala等价物:

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

不得不添加额外的val行错误我.我无法弄清楚如何声明函数arg来提取元组,所以我想知道有没有办法做到这一点,或者为什么没有foreach为我提取关键和值？

Answer 1

这也有效:

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

Answer 2

我喜欢这一个:

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

Answer 3

你甚至不需要valin for循环:

以下是ViktorKlang的例子:

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

请注意,for在Scala中相当强大,因此您也可以将它用于序列理解:

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