A better way to test the value of an Option?
I often find myself with an Option[T]
for some type T
and wish to test the value of the option against some value. For example:
val opt = Some("oxbow")
if (opt.isDefined && opt.get == "lakes")
//do something
The following code is equivalent and removes the requirement to test the existence of the value of the option
if (opt.map(_ == "lakes").getOrElse(false))
//do something
However this seems less readable to me. Other possibilities are:
if (opt.filter(_ == "lakes").isDefined)
if (opt.find(_ == "lakes").isDefined) //uses implicit conversion to Iterable
But I don't think these clearly express the intent either which would be better as:
if (opt.isDefinedAnd(_ == "lakes"))
Has anyone got 开发者_如何学JAVAa better way of doing this test?
How about
if (opt == Some("lakes"))
This expresses the intent clearly and is straight forward.
For Scala 2.11, you can use Some(foo).contains(bar)
Walter Chang FTW, but here's another awkward alternative:
Some(2) exists (_ == 2)
val opt = Some("oxbow")
opt match {
case Some("lakes") => //Doing something
case _ => //If it doesn't match
}
You can use for-comprehension as well:
for {val v <- opt if v == "lakes"}
// do smth with v
I think pattern matching could also be used. That way you extract the interesting value directly:
val opt = Some("oxbow")
opt match {
case Some(value) => println(value) //Doing something
}
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