如何在Scala中过滤Seq

Question

I have a question, I have a Scala Seq of Fruit Objects, where the name member variable of the object is the name of the fruit like

fruits: Seq[Fruit] = List(banana, apple, jackfruit, pineapple, grapes, watermelon, papaya, orange, pomegranate, strawberry)

and I have a scala String which contains the name of the fruit separated by comma like

val ilike = "apple, grapes, watermelon, guava"

I need to filter the above Seq such that it contain only the objects of Fruit I like, that is the result should be,

fruits: Seq[Fruit] = List(apple, grapes, watermelon)

I tried the Java way, but I am interested how to work the same in the Scala way. I googled a bit but I couldn't find the correct answer.

Thank You for your help in advance.

Answer 1

Just using ilike.contains as the filter function fails if ilike contains a name whose substring is in fruit :

scala> val ilike = "pineapple, grapes, watermelon, guava"
ilike: String = pineapple, grapes, watermelon, guava

scala> fruits.filter(ilike.contains)
res1: Seq[String] = List(apple, pineapple, grapes, watermelon)

Therefore, ilike should first be split into a sequence of preferences:

scala> val like = ilike.split(", ")
like: Array[String] = Array(pineapple, grapes, watermelon, guava)

Now it's safe to use like.contains for filtering:

scala> fruits.filter(like.contains)
res3: Seq[String] = List(pineapple, grapes, watermelon)

Edit: If fruits contains a list of Fruit instances with a name member, just use

scala> fruits.filter(f => like.contains(f.name)
res3: Seq[Fruit] = List(pineapple, grapes, watermelon)

Answer 2

An even more succinct way - use intersect

scala> val like = ilike.split(", ")
like: Array[String] = Array(pineapple, grapes, watermelon, guava)

scala> fruits.intersect(like)
res1: Seq[String] = List(pineapple, grapes, watermelon)

Answer 3

很简单：

  fruits.filter(f=>ilike.split(",").contains(f.name))

Answer 4

Can this be the correct answer, considering 1. the val ilike can be empty. If it is empty the return Seq should be fruits. 2. the val ilike can be seperated by a comma or a comma and space.

if(ilike != "") {
  val like = for(i <- ilike.split(",")) yield i.trim
  fruits.filter(f => like.contains(f.name))
} else {
  fruits
}