比较 Scala 中的两个 Map
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Compare two Maps in Scala
提问by sparkr
Is there any pre-defined function that I can use to compare two Maps based on the key and give me the difference? Right now, I iterate Map1 and foreach key, I check if there is an element in Map2 and I pattern match to find the difference. Is there a much elegant way to do this?
是否有任何预定义的函数可用于根据键比较两个 Map 并给出差异？现在，我迭代 Map1 和 foreach 键，我检查 Map2 中是否有一个元素，并通过模式匹配找到差异。有没有一种非常优雅的方法来做到这一点？
回答by elm
Consider the difference between the maps converted into sets of tuples,
考虑转换成元组集的映射之间的差异，
(m1.toSet diff m2.toSet).toMap
回答by Jean Logeart
Try:
尝试：
val diff = (m1.keySet -- m2.keySet) ++ (m2.keySet -- m1.keySet)
diffcontains the elements that are in m1and not in m2and that are in m2and not in m1.
diff包含的中的元素m1，而不是在m2与那些在m2和不在m1。
回答by Nikita Zonov
This solution looks like right way:
这个解决方案看起来像正确的方式：
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)
Found it here https://gist.github.com/frgomes/69068062e7849dfe9d5a53bd3543fb81
在这里找到它https://gist.github.com/frgomes/69068062e7849dfe9d5a53bd3543fb81
回答by Nate Whittaker
I think the --operator will do what you're looking for: http://www.scala-lang.org/api/current/index.html#scala.collection.Map@--(xs:scala.collection.GenTraversableOnce[A]):Repr
我认为--运营商会做你正在寻找的：http: //www.scala-lang.org/api/current/index.html#scala.collection.Map@--(xs:scala.collection.GenTraversableOnce[ A]):Repr
Although this will probably only work given the assumption that Map2 is always a subset of Map1...
尽管这可能仅在假设 Map2 始终是 Map1 的子集的情况下才有效......
