scala 如何从scala中的地图中删除键值
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how to remove key value from map in scala
提问by Govind Singh
Map(data -> "sumi", rel -> 2, privacy -> 0, status -> 1,name->"govind singh")
how to remove data from this map , if privacy is 0.
如果隐私为 0，如何从此地图中删除数据。
Map(rel -> 2, privacy -> 0, status -> 1,name->"govind singh")
回答by Leo
If you use immutable maps, you can use the -method to create a new map without the given key:
如果使用不可变映射，则可以使用该-方法在没有给定键的情况下创建新映射：
val mx = Map("data" -> "sumi", "rel" -> 2, "privacy" -> 0)
val m = mx("privacy") match {
case 0 => mx - "data"
case _ => mx
}
=> m: scala.collection.immutable.Map[String,Any] = Map(rel -> 2, privacy -> 0)
If you use mutable maps, you can just remove a key with either -=or remove.
如果您使用可变映射，则可以使用-=或删除键remove。
回答by Kevin Wright
If you're looking to scale this up and remove multiple members, then filterKeysis your best bet:
如果您希望扩大规模并删除多个成员，那么filterKeys您最好的选择是：
val a = Map(
"data" -> "sumi",
"rel" -> "2",
"privacy" -> "0",
"status" -> "1",
"name" -> "govind singh"
)
val b = a.filterKeys(_ != "data")
回答by Sudeep Juvekar
That depends on the type of Scala.collection Map you are using. Scala comes with both mutableand immutableMaps. Checks these links:
这取决于您使用的 Scala.collection Map 类型。Scala 带有mutable和immutableMaps。检查这些链接：
http://www.scala-lang.org/api/2.10.2/index.html#scala.collection.immutable.Map
http://www.scala-lang.org/api/2.10.2/index.html#scala.collection.immutable.Map
and
和
http://www.scala-lang.org/api/2.10.2/index.html#scala.collection.mutable.Map
http://www.scala-lang.org/api/2.10.2/index.html#scala.collection.mutable.Map
In both types of maps, -is usually the operation to remove a key. The details depend on the type of map. A mutablemap can be modified in place by using -=. Something like
在这两种类型的映射中，-通常是删除一个键的操作。详细信息取决于地图类型。甲mutable地图来代替通过使用进行修改-=。就像是
if (m.contains("privacy") && m.getOrElse("privacy", 1) == 0) {
m -= "play"
}
On the other hand, an immutable map can not be modified in place and has to return a new map after removing an element.
另一方面，不可变映射不能就地修改，必须在删除元素后返回新映射。
if (m.contains("privacy") && m.getOrElse("privacy", 1) == 0) {
val newM = m - "play"
}
Notice that you are creating a new immutable map.
请注意，您正在创建一个新的不可变映射。
回答by RAGHHURAAMM
val m = Map("data" -> "sumi", "rel" -> 2, "privacy" -> 0,"status" -> 1,"name"->"govind singh")
scala> if(m("privacy")==0) m.filterKeys(_ != "data")
res63: Any = Map(name -> govind singh, rel -> 2, privacy -> 0, status -> 1)
