Terraform - if within for_each. Can I filter for_each?

Question

With the following I can loop through a resource block to add route table associations to "all" of my subnets easily. However I need to create associations only for my public subnets.

How can I make this "if" statement work? Or any other way to filter on each.value.class == "pub" for that matter.

resource "aws_route_table_association" "rtb-pub" {
  for_each =  local.subnets_map 
  if each.value.class == "pub"    ## <---- how?

  route_table_id = aws_route_table.rtb-pub.id
  subnet_id      = aws_subnet.map["${each.value.subnet}"].id
}

Thanks in advance!

Answer 1

It depends on exactly what is the structure of your local.subnets_map. But the for_each should be something like the following one:

resource "aws_route_table_association" "rtb-pub" {

  for_each =  {for key, val in local.subnets_map: 
               key => val if val.class == "pub"}

  route_table_id = aws_route_table.rtb-pub.id
  subnet_id      = aws_subnet.map["${each.value.subnet}"].id
}