Are Maybes a good pattern for scala?

Question

For a while I have been struggling to integrate scala with java methods that might return null. I came up with the following utility which helps a lot:

// produce an Option, nulls become None
object Maybe {
    def apply[T](t:T) = if (t==null) None else Some(t)
}

Maybe(javaClass.getResultCouldBeNull()).map( result => doSomeWork(result) )

I have a few questions about this solution:

Is there a better or more standard pattern to use?
Am I duplicating something that already exists?
Does this functionality have hidden gotchas?

Thanks! I've been working in 2.7 and didn't realize that Option.apply() existed in 2.8. — Fred Haslam, Jun 01 '10 at 17:49

Randall Schulz · Accepted Answer · 2010-06-01T01:40:39.787

8

Scala's built-in Option is what you're setting out to reinvent.

In that case:

scala> val sOpt: Option[String] = Option(null)
sOpt: Option[String] = None

edited Jun 01 '10 at 01:40

answered Jun 01 '10 at 01:23

Randall Schulz

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He knows about the Option class already. He wants a function that makes the conversion easy. – Ken Bloom Jun 01 '10 at 01:32
`val sOpt1: Option [String] = None` and `val sOpt2: Option [String] = Some ("foo")` should do it. – user unknown Jun 01 '10 at 02:12
better: `def mb (s: String) : Option [String] = if (s != null) Some (s) else None` would do it on 2.7.7 – user unknown Jun 01 '10 at 02:27
2

@Thomas: So many things are so much better in 2.8. This is just one among many. – Randall Schulz Jun 01 '10 at 02:44
@Randall Can't wait for it to come out. But since I have a application in "production", I'm still on 2.7.7. – Thomas Jun 01 '10 at 12:46

score 1 · Answer 2 · answered Jun 01 '10 at 01:30

Why bother making a whole companion object out of it? It's just a function, so you don't need to implement it as an object that looks like a function.

object MyUtilities{
  // a whole bunch of other utilities that you use all over can also be put in this class.
  def maybe[T](t:T) = if (t==null) None else Some(t)
}

Are Maybes a good pattern for scala?

2 Answers2