Iterator variable in Terraform - Mini Project: Build & Apply

Iterator Variable in Terraform

📖 Scenario: You are setting up a simple cloud infrastructure using Terraform. You want to create multiple virtual machines (VMs) with specific names and sizes.

🎯 Goal: Build a Terraform configuration that uses an iterator variable to create multiple VMs with different names and sizes.

📋 What You'll Learn

Create a variable called vm_specs as a list of maps with exact entries

Create a local variable called vm_names that extracts VM names from vm_specs

Use a for expression with an iterator variable spec to create a map of VM sizes keyed by VM names

Define a resource azurerm_virtual_machine using the iterator variable spec in a for_each block

💡 Why This Matters

🌍 Real World

This project shows how to use iterator variables in Terraform to manage multiple cloud resources efficiently.

💼 Career

Understanding iterator variables is essential for cloud engineers to write scalable and maintainable infrastructure code.

1

Create the VM specifications variable

Create a Terraform variable called vm_specs as a list of maps with these exact entries: { name = "vm1", size = "Standard_B1s" }, { name = "vm2", size = "Standard_B2s" }, and { name = "vm3", size = "Standard_B1ms" }.

Terraform

# Your code here

Need a hint?

Define a variable with type list of objects containing name and size keys.

2

Create a local variable for VM names

Create a local variable called vm_names that extracts the name from each element in the var.vm_specs list using a for expression with iterator variable spec.

Terraform

variable "vm_specs" {
  type = list(object({
    name = string
    size = string
  }))
  default = [
    { name = "vm1", size = "Standard_B1s" },
    { name = "vm2", size = "Standard_B2s" },
    { name = "vm3", size = "Standard_B1ms" }
  ]
}

# Your code here

Need a hint?

Use a for expression with spec as iterator to get names.

3

Create a map of VM sizes keyed by VM names

Create a local variable called vm_sizes_map that uses a for expression with iterator variable spec over var.vm_specs to create a map where keys are spec.name and values are spec.size.

Terraform

variable "vm_specs" {
  type = list(object({
    name = string
    size = string
  }))
  default = [
    { name = "vm1", size = "Standard_B1s" },
    { name = "vm2", size = "Standard_B2s" },
    { name = "vm3", size = "Standard_B1ms" }
  ]
}

locals {
  vm_names = [for spec in var.vm_specs : spec.name]
  # Your code here
}

Need a hint?

Use a for expression with spec to build a map of names to sizes.

4

Define VM resources using the iterator variable

Define a resource block resource "azurerm_virtual_machine" "example" that uses for_each = { for spec in var.vm_specs : spec.name => spec }. Inside the resource, set name = each.key and vm_size = each.value.size to use the iterator variable spec indirectly via each.

Terraform

variable "vm_specs" {
  type = list(object({
    name = string
    size = string
  }))
  default = [
    { name = "vm1", size = "Standard_B1s" },
    { name = "vm2", size = "Standard_B2s" },
    { name = "vm3", size = "Standard_B1ms" }
  ]
}

locals {
  vm_names = [for spec in var.vm_specs : spec.name]
  vm_sizes_map = { for spec in var.vm_specs : spec.name => spec.size }
}

# Your code here

Need a hint?

Use for_each with a map from spec.name to spec. Use each.key and each.value.size inside the resource.