Scala 地图转换
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/2894862/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Scala Map conversion
提问by Vonn
I'm a Scala newbie I'm afraid: I'm trying to convert a Map to a new Map based on some simple logic:
恐怕我是 Scala 新手：我正在尝试根据一些简单的逻辑将 Map 转换为新 Map：
val postVals = Map("test" -> "testing1", "test2" -> "testing2", "test3" -> "testing3")
I want to test for value "testing1" and change the value (while creating a new Map)
我想测试值“testing1”并更改值（在创建新地图时）
def modMap(postVals: Map[String, String]): Map[String, String] = {
postVals foreach {case(k, v) => if(v=="testing1") postVals.update(k, "new value")}
}
回答by Arjan Blokzijl
You could use the 'map' method. That returns a new collection by applying the given function to all elements of it:
您可以使用“地图”方法。通过将给定的函数应用于它的所有元素来返回一个新集合：
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))
回答by missingfaktor
Alternative to Arjan's answer: (just a slight change)
替代 Arjan 的答案：（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)
回答by gun
even easier:
更简单：
val myMap = Map("a" -> "apple", "b" -> "banana")
myMap map {
case (k, "apple") => (k, "apfel")
case pair => pair
}
