问题描述
sealed class A
class B1 extends A
class B2 extends A
假设我们有一个类A的对象的列表: val l:List [A] = List(新B1，新B2，新B1，新B1)
Assuming we have a List of objects of class A : val l: List[A] = List(new B1, new B2, new B1, new B1)
我们要过滤掉B1类型的元素.然后我们需要一个谓词，并可以使用以下两种替代方法:
And we want to filter out the elements of the type B1.Then we need a predicate and could use the following two alternatives:
l.filter(_.isInstanceOf[B1])
或
l.filter(_ match {case b: B1 => true; case _ => false})
我个人更喜欢第一种方法，但是我经常阅读，应该更频繁地使用match-case语句(出于我不知道的原因).
Personally, I like the first approach more, but I often read, one should use the match-case statement more often (for reasons I do not know).
因此，问题是:使用isInstanceOf而不是match-case语句是否有缺点?什么时候应该使用哪种方法(以及在这里应该使用哪种方法，为什么?)?
Therefore, the question is: Are there drawbacks of using isInstanceOf instead of the match-case statement ? When should one use which approach (and which approach should be used here and why) ?
推荐答案
您可以像这样进行过滤:
You can filter like that:
l.collect{ case x: B1 => x }
IMO更具可读性.
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