Check if a string is blank or doesn't exist in Scala
Solution 1
What you should do is check using exists
. Like so:
myOption.exists(_.trim.nonEmpty)
which will return True
if and only if the Option[String]
is not None
and not empty.
Solution 2
An approach based in pattern matching,
def isBlank( input : Option[String]) : Boolean =
input match {
case None => true
case Some(s) => s.trim.isEmpty
}
Solution 3
exists
(Accepted solution) will work when input has at least one element in it, that is Some("")
but not when it's None
.
exists
checks if at least one element(x
) applies to function.
eg.
scala> List[String]("apple", "").exists(_.isEmpty)
res21: Boolean = true
//if theres no element then obviously returns false
scala> List[String]().exists(_.isEmpty)
res30: Boolean = false
Same happens with Option.empty
, as theres no element in it,
scala> Option.empty[String].exists(_.isEmpty)
res33: Boolean = false
So forall
is what makes sure the the function applies all the elements.
scala> def isEmpty(sOpt: Option[String]) = sOpt.forall(_.trim.isEmpty)
isEmpty: (sOpt: Option[String])Boolean
scala> isEmpty(Some(""))
res10: Boolean = true
scala> isEmpty(Some("non-empty"))
res11: Boolean = false
scala> isEmpty(Option(null))
res12: Boolean = true
The gross way is to filter nonEmpty
string, then check option.isEmpty
.
scala> def isEmpty(sOpt: Option[String]) = sOpt.filter(_.trim.nonEmpty).isEmpty
isEmpty: (sOpt: Option[String])Boolean
scala> isEmpty(None)
res20: Boolean = true
scala> isEmpty(Some(""))
res21: Boolean = true
Solution 4
This should work as well since filter of an empty Option results in an empty Option
def isBlank( input : Option[String]) : Boolean =
input.filter(_.trim.length > 0).isEmpty
Solution 5
All proposed solutions will crash with NullPointerException if you pass:
val str : Option[String] = Some(null).
Therefore null-check is a must:
def isBlank(input: Option[String]): Boolean =
input.filterNot(s => s == null || s.trim.isEmpty).isEmpty
Soumya Simanta
Updated on January 21, 2020Comments
-
Soumya Simanta over 4 years
I have an
Option[String]
.I want to check if there is a string exists and if it's exists its not blank.
def isBlank( input : Option[String]) : Boolean = { input.isEmpty || input.filter(_.trim.length > 0).isEmpty }
Is there is a better way of doing this in Scala ?