Scala for comprehension - yield w/ a complex filter

Question

I'm in the process of trying to build a for comprehension in Scala, but am running into some issues when I try to use a more complex filter.

I'm aware of basic for comprehension filtering:

for (x <- 1 until 20 if x>3) yield {
  x
}

However, I want to build a for comprehension which has a much more complex filtering statement. For example, here's an illustrative version of what I'm trying to do:

for (
    element <- elementList
    val otherElement = databaseCall.getMatching(element.id)
    if element.name==otherElement.name
) yield {
  element
}

Basically, if you want to do a filter with some more complex requirements, this gets awkward, because the for comprehensions don't allow declaring vals in the filter statement, and you'd otherwise have to fit that all one one line.

An alternative would be to not use the filter mechanism at all, and just yield either Some(element) or None, and end up with an Option[elementType] list instead. However, I don't want to have Optional types in this case.

Imperatively, I'd simply create a mutable list, and only append to the list when my condition is met, but I want to see how to do this in more of a declarative manner (not all of the way declarative yet, but I'm still learning!).

Any suggestions of good declarative ways to do this would be hugely helpful.

Answer 1

Is using the filter method of List not the simplest solution in this case?:

elementList.filter(el => databaseCall.getMatching(el.id).name == el.name)