[英]Spark/Scala iterator unable to assign variables defined outside of foreach loop
[英]assign value in scala foreach loop
我正在學習scala,但陷入了一個簡單的問題。 我想使用foreach循環為變量分配一個值。
例如:
List A
foreach x in A { variable b = x; => then some operation => print result}
您能告訴我如何在Scala中實現這一目標嗎?
1)如果要處理.map
並希望返回其他list
則可以在list
上使用.map
(就像在數學f:A => B中一樣)
輸入集
scala> val initialOrders = List("order1", "order2", "order3")
initialOrders: List[String] = List(order1, order2, order3)
功能
scala> def shipOrder(order: Any) = order + " is shipped"
shipOrder: (order: Any)String
處理輸入集並存儲輸出
scala> val shippedOrders = initialOrders.map(order => { val myorder = "my" + order; println(s"shipping is ${myorder}"); shipOrder(myorder) })
shipping is myorder1
shipping is myorder2
shipping is myorder3
shippedOrders: List[String] = List(myorder1 is shipped, myorder2 is shipped, myorder3 is shipped)
2)或者,當您不關心函數的輸出時,也可以簡單地使用列表中的foreach
進行迭代。
scala> initialOrders.foreach(order => { val whateverVariable = order+ "-whatever"; shipOrder(order) })
注意
這是在列表上運行foreach操作的正確方法。
val list: List[T] = /* list definition */
list foreach { x => var a = x; /* some operation */ }
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