如何解释Map.map结果 [英] How to explain Map.map result

问题描述

当我查看 Map.map scaladoc时，可以看到

When I look a the Map.map scaladoc, I can see

map[B](f: (A) ⇒ B): Map[B]

但是下面的简单代码不会返回 Map

But the simple following code doesn't return a Map

scala> Map("answer" -> 42).map { case(k, v) => v }
res40: scala.collection.immutable.Iterable[Int] = List(42)

您能解释吗？

推荐答案

Scaladocs是简化的，如果要查看完整的签名，则必须展开并单击显示完整的签名，您会看到真正的签名是这样的：

Scaladocs are simplified, if you want to see the full signature you have to expand and click on show full signature and you'll see that the real one is this:

def map[B, That](f: ((A, B)) ⇒ B)(implicit bf: CanBuildFrom[Map[A, B], B, That]): That

哪个可以返回那个，可以是 Map ，也可以是列表。

Which allows to return a That which can be a Map but also a List.

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