在scala foreach循环中分配值

Question

I am learning scala but got stuck in a simple problem. I wanted to assign a value to a variable using foreach loop.

for example:

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

can you please let me know how I can achieve this in scala?

Answer 1

1) You can use .map on list if you want to process it and want a list of something else back (just like in maths f:A=>B)

input set

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

function

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

process input set and store output

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) Or you can simply iterate with foreach on list when you don't care about output from function.

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

Note

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

Answer 2

this is proper way of running a foreach operation on a List.

val list: List[T] = /* list definition */
list foreach { x => var a = x; /* some operation */ }