斯卡拉地图转换

Question

我是一个新手斯卡拉恐怕： 我想一个地图转换成基于一些简单的逻辑新地图：

val postVals = Map("test" -> "testing1", "test2" -> "testing2", "test3" -> "testing3") 

我想测试值“ testing1" 并更改值（在创建新地图）

def modMap(postVals: Map[String, String]): Map[String, String] = { 
    postVals foreach {case(k, v) => if(v=="testing1") postVals.update(k, "new value")} 
} 

Answer 1

您可以使用‘映射’的方法。

scala> def modMap(postVals: Map[String, String]): Map[String, String] = { 
    postVals map {case(k, v) => if(v == "a") (k -> "other value") else (k ->v)} 
} 

scala> val m = Map[String, String]("1" -> "a", "2" -> "b") 
m: scala.collection.immutable.Map[String,String] = Map((1,a), (2,b)) 

scala> modMap(m) 
res1: Map[String,String] = Map((1,other value), (2,b)) 

Answer 2

替代阿尔扬的回答是：：（只是略有变化）

scala> val someMap = Map("a" -> "apple", "b" -> "banana") 
someMap: scala.collection.immutable.Map[java.lang.String,java.lang.String] = Map(a -> apple, b -> banana) 

scala> val newMap = someMap map {          
    | case(k , v @ "apple") => (k, "alligator")    
    | case pair    => pair    
    | } 
newMap: scala.collection.immutable.Map[java.lang.String,java.lang.String] = Map(a -> alligator, b -> banana) 

Answer 3

更容易：

val myMap = Map("a" -> "apple", "b" -> "banana") 

myMap map { 
    case (k, "apple") => (k, "apfel") 
    case pair => pair 
}