Scala For Comprehension with Filter - scala

Question

I am using Scala's for comprehension to produce a modified facetFilter. If a value in facetFilter doesn't exist in allFacets, it should be filtered out. Currently, the newFacetFilter doesn't filter at all.
val allFacets = Map(
"band_material" -> Map("Rubber" -> 11),
"dial_color" -> Map("Ivory" -> 68, "Salmon"-> 3))
val facetFilter =
Map("band_material" -> List("Yellow Gold Plated", "Rubber"),
"dial_color" -> List("Ivory"))
val newFacetFilter =
for {
(k,v) <- allFacets
(facetName, facetArr) <- facetFilter
aFacet <- facetArr
if k != facetName || !v.contains(aFacet)
} yield (facetName -> facetArr)
Current Output of newFacetFilter:
Map("band_material" -> List("Yellow Gold Plated", "Rubber"), "dial_color" -> List("Ivory"))
Expected Output of newFacetFilter:
Map("band_material" -> List("Rubber"), "dial_color" -> List("Ivory"))
See this fiddle

Answer 1

Try this:
val newFacetFilter =
for ((k,vs) <- facetFilter)
yield (k, vs filter allFacets(k).contains)
Output:
Map(band_material -> List(Rubber), dial_color -> List(Ivory))

Answer 2

OK, if we are done with edits, I think this is what you want...
val allFacets = Map(
"band_material" -> Map(
"Rubber" -> 11
),
"dial_color" -> Map(
"Ivory" -> 68,
"Salmon"-> 3
)
)
val facetFilter = Map(
"band_material" -> List("Yellow Gold Plated", "Rubber"),
"dial_color" -> List("Ivory"),
"case_material" -> List(),
"movement" -> List(),
"price_range" -> List(),
"gender" -> List()
)
val newFacetFilter = for {
(facetName, facetArr) <- facetFilter
(k,v) <- allFacets
if k == facetName
} yield (facetName, facetArr intersect v.keys.toList)
We simply iterate both maps and when we have the same keys, we intersect the two lists.
Edit: There is a more efficient way, using the Map's get function instead of just iterating everything and ignoring non-matches.
val newFacetFilter = facetFilter.flatMap {
case (n, fs) =>
allFacets.get(n).map(n -> _.keys.toList.intersect(fs))
}
So we take each facetFilter entry ((n, fs)), check allFacets for n, then intersect the optional result with our list fs. If n did not exist, we propagate None and it is flattened out by flatMap.