在scala foreach循環中分配值

Question

我在學習scala，但陷入了一個簡單的問題。我想使用foreach循環爲變量賦值。

例如：

List A 
foreach x in A { variable b = x; => then some operation => print result} 

可以請你讓我知道我可以在Scala中實現這一目標？

Answer 1

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 */ } 

Answer 2

1）您可以使用list.map如果你要處理它，想別的事情列表回（就像數學F：A => B）

輸入集

scala> val initialOrders = List("order1", "order2", "order3") 
initialOrders: List[String] = List(order1, order2, order3) 

功能

個

scala> def shipOrder(order: Any) = order + " is shipped" 
shipOrder: (order: Any)String 

過程輸入設置並存儲輸出

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），也可以用foreach名錄簡單重複，當你不關心從功能輸出。

scala> initialOrders.foreach(order => { val whateverVariable = order+ "-whatever"; shipOrder(order) }) 

注意

What is the difference between a var and val definition in Scala?