scala 两个条件下的Scala过滤器
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Scala filter on two conditions
提问by richsoni
I would like to filter my data set on two conditions at once.
我想一次在两个条件下过滤我的数据集。
Is it possible?
是否可以？
I want something like this:
我想要这样的东西：
mystuff = mystuff.filter(_.isX && _.name == "xyz")
回答by Alex Wilson
回答by Dave Griffith
While there might be some performance impact depending on what "myStuff" is, you could always filter twice
虽然根据“myStuff”的含义可能会对性能产生一些影响，但您始终可以过滤两次
mystuff = mystuff.filter(_.isX).filter(_.name == "xyz")
回答by paradigmatic
If you need to frequently filter with several predicate, you could define a way of combining them:
如果您需要经常使用多个谓词进行过滤，您可以定义一种组合方式：
case class And[A]( p1: A=>Boolean, p2: A=>Boolean ) extends (A=>Boolean) {
def apply( a: A ) = p1(a) && p2(a)
}
Here is how to use it to keep only the odd numbers bigger than 10:
以下是如何使用它来仅保留大于 10 的奇数：
scala> (0 until 20) filter And( _ > 10, _ % 2 == 1 )
res3: scala.collection.immutable.IndexedSeq[Int] = Vector(11, 13, 15, 17, 19)
It easy to write Orand Notcombinators in the same fashion.
以相同的方式编写Or和Not组合器很容易。
