Filter a string before creating an Option[String]

I have the following where obj is a JsObject:

val approx_pieces: Option[String] = (obj \ "approx_pieces").asOpt[String]

This code will create a Some("0") if the approx pieces is "0" in the database.

How can I change it so that it creates None when the string is "0"?

If you already have an Option, and you don't want to use the value in certain cases, then filter is your most idiomatic choice:

val one = Option("1")
val zero = Option("0")
one.filter(_ != "0") //Some("1")
zero.filter(_ != "0") //None

Using this method, your solution would be:

(obj \ "approx_pieces").asOpt[String].filter(_ != "0")

Alternatively, you can do this with a match statement. The JsValue subtypes in Play all have an unapply method, so you can directly match on them:

(obj \ "approx_pieces") match {
    case JsString(num) if num != "0" => Some(num)
    case _ => None
}

You might also be interested in the collect method:

(obj \ "approx_pieces").asOpt[String] collect {
    case num if num != "0" => num
}

collect is nice because it allows you to filter and map at the same time.

You can use both of the above methods together, too:

Option(obj \ "approx_pieces") collect {
    case JsString(num) if num != "0" => num
}