比较Scala中的两个map

Question

是否有任何预定义的函数，我可以使用它来比较基于键的两个map并给出我的差异?现在，我迭代Map1并查找每个键，检查Map2中是否有元素，并进行模式匹配以查找差异。是否有更优雅的方法来做到这一点?

Answer 1

考虑转换为元组集合的映射之间的差异，

(m1.toSet diff m2.toSet).toMap

Answer 2

尝试:

val diff = (m1.keySet -- m2.keySet) ++ (m2.keySet -- m1.keySet)

diff含有m1中不含m2的元素和m2中不含m1的元素。

Answer 3

这个解决方案看起来是正确的:

scala> val x = Map(1 -> "a", 2 -> "b", 3 -> "c")
x: scala.collection.immutable.Map[Int,String] = Map(1 -> a, 2 -> b, 3 -> c)
scala> val y = Map(1 -> "a", 2 -> "b", 4 -> "d")
y: scala.collection.immutable.Map[Int,String] = Map(1 -> a, 2 -> b, 4 -> d)
scala> val diff : Map[Int, String] = x -- y.keySet
diff: Map[Int,String] = Map(3 -> c)

在这里找到https://gist.github.com/frgomes/69068062e7849dfe9d5a53bd3543fb81

Answer 4

我认为--操作符会做你正在寻找的:http://www.scala-lang.org/api/current/index.html#scala.collection.Map@—(xs:scala.collection.GenTraversableOnce[A]):Repr

虽然这可能只在假设Map2总是Map1的子集的情况下才有效…