[英]Spark/Scala iterator unable to assign variables defined outside of foreach loop
[英]assign value in scala foreach loop
我正在学习scala,但陷入了一个简单的问题。 我想使用foreach循环为变量分配一个值。
例如:
List A
foreach x in A { variable b = x; => then some operation => print result}
您能告诉我如何在Scala中实现这一目标吗?
1)如果要处理.map
并希望返回其他list
则可以在list
上使用.map
(就像在数学f:A => B中一样)
输入集
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
处理输入集并存储输出
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,当您不关心函数的输出时,也可以简单地使用列表中的foreach
进行迭代。
scala> initialOrders.foreach(order => { val whateverVariable = order+ "-whatever"; shipOrder(order) })
注意
这是在列表上运行foreach操作的正确方法。
val list: List[T] = /* list definition */
list foreach { x => var a = x; /* some operation */ }
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