Initialization of class members using constructor parameters

Question

I would like to create a class that only holds single-digit numbers.

class onlyLikesSingleDigits(val anyNumber: Seq[Int]) {
  val onlySingleDigits = anyNumber.filter(_ < 10)
}

The idea is you can construct it, and any numbers greater than or equal to 10 that you pass into the constructor would just be discarded.

My implementation looks rather ugly. Can't I do this without using anyNumber? I want to initialize my class using the constructor parameters as input to the filter, not as actual members of the class.

How can I do this with only a single val?

if you want only filtered elements, why not use filtered sequence as constructor argument directly? the example is a bit artificial. — Ashalynd, Sep 30 '14 at 23:27

score 2 · Answer 1 · edited May 23 '17 at 10:26

2

Just remove val from anyNumber and it won't be member of the class. Maybe you'll find this helpful: scala class constructor parameters

edited May 23 '17 at 10:26

Community

1
1

answered Sep 30 '14 at 23:04

Sergey Lihoman

98
8

score 1 · Answer 2 · answered Oct 01 '14 at 07:07

You should better separate the data representation from constructor logic by using Factory pattern.

Data representation

scala> case class OnlyLikesSingleDigits(digits: Seq[Int])

Factory

object DigitsMaker { 
  def apply(anyNums: Seq[Int]) = OnlyLikesSingleDigits(anyNums.filter(_ < 10)) 
}

Usage

scala> val r = DigitsMaker(Seq(4, 12, 5, 76))
r: OnlyLikesSingleDigits = OnlyLikesSingleDigits(List(4, 5))

Initialization of class members using constructor parameters

2 Answers2