Cloud/Terraform/ForLoop

Loop over LIST/MAP gen MAP

• Loop over a list and output a map

{for <ITEM> in <LIST> : <OUTPUT_KEY> => <OUTPUT_VALUE>}

• Loop over a map and output a map

{for <KEY>, <VALUE> in <MAP> : <OUTPUT_KEY> => <OUTPUT_VALUE>}

Loop over LIST/MAP gen LIST

[for <ITEM> in <LIST> : <OUTPUT>]

[for <KEY>, <VALUE> in <MAP> : <OUTPUT>]

Merge List of Map(dict) into single MAP

* https://developer.hashicorp.com/terraform/language/functions/merge

* e.g. 1

> merge([{a="b", c="d"}, {}, {e="f", c="z"}]...)
{
  "a" = "b"
  "c" = "z"
  "e" = "f"
}

• e.g.2 notice the magic "..." passed to merge

    hosts = merge((
      [for k, v in var.config :
        { for host in v.backend_hosts : "${k}_${host}" => host
        }
  
      ]
    )...)

Flatten

• e.g.

  > flatten([[["a", "b"], []], ["c"]])
  ["a", "b", "c"]

Nested for loops

• nest

  locals {
    expanded_access = flatten([
      for k, v in var.access : [
        for index, role in v.role_names : {
          key   = "${k}-${replace(role, " ", "_")}"
          value = merge(v, { role = role }, {description = try(v.descriptions_role_assignment[index], null)},)
        }
      ]
    ])
  }

• use

   for_each = { for item in local.expanded_access : item.key => item.value }

Variable validation on list

Uniq

• distinct(["a","a"] = ["a"]

  • https://developer.hashicorp.com/terraform/language/functions/distinct