Say I have a function that checks whether some operation is applicable to an instance of A and, if so, returns an instance of B or None:
def checker[A,B]( a: A ) : Option[B] = ...
Now I want to form a new collection that contains all valid instances of B, dropping the None values. The following code seems to do the job, but there is certainly a better way:
val as = List[A]( a1, a2, a3, ... )
val bs =
as
.map( (a) => checker(a) ) // List[A] => List[Option[B]]
.filter( _.isDefined ) // List[Option[B]] => List[Option[B]]
.map( _.get ) // List[Option[B]] => List[B]
This should do it:
val bs = as.flatMap(checker)