Using Try[Boolean] with list iteration - scala

Question

case class Employee(name :String, dept :String, empId:String, startDate:String)
val emp1 = Employee("abc","accounts", "1234","2019-09-28")
val emp2 = Employee("def","HR", "12345","2019-09-29")
val emp3 = Employee("pp","HR", "12346", "2019-09-28")
val emp4 = Employee("xyz","accounts", "12347","2019-09-20")
val list = Seq(emp1, emp2, emp3, emp4)
def isValidDate(date: LocalDateTime, e:
Employee):Boolean={
date.isAfter(e.startDate)
}
private def test(name :String, date:String,list:Seq[Employee])={
list.exists(e =>isValidDate(LocalDate.parse(date).atStartOfDay(), e))
}
test("abc",2019-09-28, list)
test("xyz",2019-09-28, list)
test("def",2019-09-28, list)
The above works but when I change method to below
def isValidDate(date: LocalDateTime, e:
Employee):Try[Boolean]={
date.isAfter(e.startDate)
}
The below line gives compile error as it expects a boolean
list.exists(e =>isValidDate(date, e))
I want the handling of success and failure be outside isValidDate method

Answer 1

First of all, you'll need to change the implementation of isValidDate:
def isValidDate(date: LocalDateTime, e: Employee): Try[Boolean]={
Try { date.isAfter(e.startDate) }
}
Then, the implementation of your higher order function would need to deal with the Try:
private def test(name: String, date: LocalDateTime, list: Seq[Employee]) = {
list.exists(isValidDate(date, _) match {
case Failure(_) => false
case Success(value: Boolean) => value
})
}
Or as Zang proposes in the comments:
private def test(name: String, date: LocalDateTime, list: Seq[Employee]) = {
list.exists(isValidDate(date, _).getOrElse(false))
}
I would say though, that I'm not sure all this is necessary. Does isAfter throw any exception? Try is mostly used to capture exceptional code, which I don't think is the case here.

Answer 2

If you want to handle the exception outside isValidDate then there is no point in changing isValidDate, you can simply catch the exception outside. For example
private def test(name: String, date: LocalDateTime, list: Seq[Employee]) =
Try {
list.exists(e => isValidDate(date, e))
}.getOrElse(false)
This will fail the whole test if there is an exception. If you want to ignore exceptions and keep testing later employees, do this
private def test(name: String, date: LocalDateTime, list: Seq[Employee]) =
list.exists(e => Try(isValidDate(date, e)).getOrElse(false))
However in this case I believe that it better to put the exception handling in isValidDate, even though this is not what you say you want:
def isValidDate(date: LocalDateTime, e: Employee): Boolean =
Try(date.isAfter(e.startDate)).getOrElse(false)
private def test(name: String, date: LocalDateTime, list: Seq[Employee]) =
list.exists(e => isValidDate(date, e))