How to check if a variable is a list in scala: Any is list?

Question

I need something like

def isList(variable: Any): Boolean = {
  // code here for returning true or false
}

I saw this, but I cant say just "List" in this case. Compiler said List takes params. Looks like List[_] or List[Any] will work here as suggested below. — Sergey Yarotskiy, Jan 21 '15 at 19:00

score 5 · Answer 1 · answered Jan 21 '15 at 18:59

5

scala> def isList(v: Any) : Boolean = v match {
           case _: List[_] => true
           case _ => false
       }
isList: (v: Any)Boolean

scala> isList(List(1))
res0: Boolean = true

scala> isList(Array(1))
res1: Boolean = false

answered Jan 21 '15 at 18:59

Marth

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score 2 · Accepted Answer · answered Jan 21 '15 at 19:17

You can simply use isInstanceOf method


 def isList(variable: Any): Boolean =  variable.isInstanceOf[List[_]]
                                                  //> isList: (variable: Any)Boolean
  isList(List(1,2))                               //> res0: Boolean = true
  isList(1)                                       //> res1: Boolean = false
  isList(Array(1,2))                              //> res2: Boolean = false

How to check if a variable is a list in scala: Any is list?

2 Answers2