Terraform the Hardway - Loops #1

For Expressions/Loops

Different types of loops:

• count

• for expressions

• for_each meta argument

For

For loops have a core functionality to transform type values. The expression after the in keyword can either be of type list, map, or it can be a set or an object.

The syntax isn't what you'd expect if you're used to general-purpose programming languages, but just think of anything after : as what's in your curly brackets (the actual logic and what's happening in the code)

list = ["test1", "test2", "test3"]
[for s in var.list : upper(s)]

You can also add for loops as blocks.

variable "users" {
  type = map(object({
    is_admin = boolean
  }))
}

locals {
  admin_users = {
    for name, user in var.users : name => user
    if user.is_admin
  }
  regular_users = {
    for name, user in var.users : name => user
    if !user.is_admin
  }
}

For-Each

for_each feels a little bit more "human-readable" when it comes to looping.

Notice how to call the key and value in a for_each block; by using the each keyword.

resource "azurerm_resource_group" "rg" {
  for_each = {
    a_group = "eastus"
    another_group = "westus2"
  }
  name     = each.key
  location = each.value
}

Conditionals/if statements

If you're used to programming with a general-purpose programming language, you'll probably notice how if statements in Terraform aren't exactly comparable. The logic is definitely there, but it's relatively watered down if you're used to if/elif/else

The logic is CONDITION ? TRUEVAL : FALSEVAL

The "desired/true" value is on the left and the "undesired/false" value is on the right.

${var.create_elastic_ip_address == true ? 1 : 0}