Iterating through a list while already using for_each (Terraform 0.12) - amazon-web-services

Question

I'm currently trying to use TF 0.12 to create AWS Organizations accounts. Right now I have a map of accounts with applicable info, here is an example where "Services" is the account name:
accountMap = {
...
Services = {
OU = ["Development", "Production"]
},
...
}
OU refers to the org units the account should be a part of. I'm currently already using for_each to loop through this map of account names, but I'm stuck on how to use the OUs as a suffix, so the org account name would become "Services-Development" and "Services-Production". I have tried similar to the following:
resource "aws_organizations_account" "main" {
for_each = var.ouMap
name = "${each.key}-${var.accountMap["${each.value[*]}"]}"
...
}
However, "name" requires a string and I get an error since I am providing a list of the OUs, but I may want one account to belong to several OUs or just a single OU. So, how can I either convert the list to a string one at a time, while in the same for_each iteration (but for my differing OUs)?
I'm open to other suggestions on best practice to map AWS Org accounts to multiple OUs as I'm still rather new to Terraform.

Answer 1

A local value can be computed using nested for loop in terraform v0.12.
The local value can later be used in resources. This example treats a null resource.
accountMap = {
Services = {
OU = ["Development", "Production"]
}
}
locals {
organization_account = flatten(
[for k, v in var.accountMap: [for v2 in v.OU: "${k}-${v2}"]]
)
}
resource "null_resource" "foo" {
count = length(local.organization_account)
provisioner "local-exec" {
command = "echo ${local.organization_account[count.index]}"
}
}
output "organization_account" {
value = local.organization_account
}