Option in the Scala language is a container for zero or one element of a given type.
Option in scala is a container for zero or one element of a given type.
Questions tagged [scala-option]
232 questions
11
votes
2 answers
Proper way to construct Option object: Option(value) vs Some(value)
What is the pros and cons of 2 ways of initiating Option objects:
1.
def getAmount: Option[Int] = {
val a: Int = 1
Option(a)
}
2.
def getAmount: Option[Int] = {
val a: Int = 1
Some(a)
}
Which should I use?
WelcomeTo
- 19,843
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11
votes
2 answers
Scala: How can I explicitly compare two Options?
If I have two Options such as
val a = Option(2)
val b = Option(1)
I can write
List(a,b).sorted
and it sorts correctly by inserting an implicit Ordering. How can I get a reference to this Ordering so I can call compare(a,b) and get the result? I'd…
Sam
- 1,260
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11
votes
3 answers
Slick left outer join fetching whole joined row as option
My join looks like this:
def byIdWithImage = for {
userId <- Parameters[Long]
(user, image) <- Users leftJoin RemoteImages on (_.imageId === _.id) if user.id === userId
} yield (user, image)
but slick fails at runtime when user.imageId is…
Somatik
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11
votes
9 answers
How do I find the min() or max() of two Option[Int]
How would you find minValue below?
I have my own solution but want to see how others would do it.
val i1: Option[Int] = ...
val i2: Option[Int] = ...
val defaultValue: Int = ...
val minValue = ?
Graham Lea
- 5,797
- 3
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10
votes
2 answers
Scala: Does Option[Boolean] makes sense?
So an Option[Int] or Option[String] or for that matter Option[A] results in Some(A) or None, but a Boolean is different as it inherently represents dual states (true/false), does it makes sense to have Option[Boolean]? I face this frequently when a…
iyerland
- 632
- 2
- 10
- 24
9
votes
3 answers
Method call with option value or default parameter in Scala
I'm rather new to Scala and stumbled upon a small little issue that keeps bothering me. Let's say there is some method with default parameter
def foo(v: Any = "default"): String = s"called with parameter '$v'"
and an Option val opt:…
ABika
- 597
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- 11
9
votes
3 answers
Scala for comprehension with future and options
object Main extends App {
val p1 = Promise[Option[String]]()
val p2 = Promise[Option[String]]()
val f1 = p1.future
val f2 = p2.future
val res = (for{
file1Opt <- f1
file2Opt <- f2
file1 <- file1Opt
file2 <- file2Opt
}…
An Illusion
- 769
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8
votes
1 answer
Methods versus Function and implicits in Scala
Let's declare a def and an equivalent function as a val:
scala> def optional(x:Int):Option[String] = None
optional: (x: Int)Option[String]
scala> val optional2:(Int)=>Option[String] = (i:Int) => None
optional2: Int => Option[String] =…
Kim Stebel
- 41,826
- 12
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8
votes
3 answers
Examples of using some Scala Option methods
I have read the blog post recommended me here. Now I wonder what some those methods are useful for. Can you show examples of using forall (as opposed to foreach) and toList of Option?
Michael
- 10,185
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8
votes
2 answers
Why does the Option's orNull method have this superfluous implicit argument?
I wonder what is the reason for the (implicit ev: Null <:< A1) here:
sealed abstract class Option[+A] extends Product with Serializable {
def orNull[A1 >: A](implicit ev: Null <:< A1): A1 = this getOrElse null
...
}
Wouldn't
def orNull[A]: A…
soc
- 27,983
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8
votes
4 answers
How can I reverse of flow of Option Monad?
say, I have a bunch of "validation" functions that return None if there is no error, otherwise it return Some(String) specifying the error message. Something like the following ...
def validate1:Option[String]
def validate2:Option[String]
def…
sanjib
- 593
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8
votes
4 answers
Avoiding deeply nested Option cascades in Scala
Say I have three database access functions foo, bar, and baz that can each return Option[A] where A is some model class, and the calls depend on each other.
I would like to call the functions sequentially and in each case, return an appropriate…
Ralph
- 31,584
- 38
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- 282
8
votes
4 answers
Handle Scala Option idiomatically
What is the more idiomatic way to handle an Option, map / getOrElse, or match?
val x = option map {
value => Math.cos(value) + Math.sin(value)
} getOrElse {
.5
}
or
val x = option match {
case Some(value) => Math.cos(value) +…
Paul Draper
- 78,542
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7
votes
4 answers
How do I pull apart Case Classes filled with Options in Scala
I'm very new to Scala and I'm still trying to get used to the syntax and style, so this is probably a very simple question.
I'm working with a codebase where there are lots of case classes populated with Options like so:
case class Person(
pants:…
Adam Fraser
- 6,255
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- 54
7
votes
2 answers
Processing optional xml attributes in Scala
I have code that reads an XML file. Some of the attributes of elements that I need to process are optional. I am trying to use Option[T] to manage them. I have written the following to pimp the NodeSeq type returned by the \ Node operator:
class…
Ralph
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