Terraform type constraints or variable types

#terraform #aws #tutorial #beginners

Day 7 of #30daysofawsterraform challenge

Today I come across different types of variables in Terraform.

$ What is variables in Terraform?
Variables in Terraform are like placeholders that store values, this makes your code reusable across environments (dev, staging, prod) and teams.

$ Types:

Basic Types:

String - Text values Eg: variable "environment" { default = "dev" type = string

Access using:
Environment = var.environment

Number - Numeric values (integers and floats) Eg: variable "instance_count" { description = "Number of instances to create" type = number }

Access using:
count = var.instance_count

Bool - Boolean values (true/false)
Eg:
variable "monitoring_enabled" {
description = "Enabled detailed monitoring for EC2 instance"
type = bool
default = true
}

Access using:
monitoring = var.monitoring_enabled

Collection Types:

List(type) - Ordered collection of values Eg: variable "cidr_block" { description = "CIDR block for VPC" type = list(string) default = ["10.0.0.0/8", "192.168.0.0/16", "172.16.0.0/12"] }

Access using:
cidr_ipv4 = var.cidr_block[2]

Set(type) -
Unordered collection of unique values
Do not allow the duplicates
It cannot access by their index - first convert it into list and then access the data.

Eg:
variable "allowed_region" {
description = "AWS list of allowed regions"
type = set(string)
default = ["us-east-1", "us-west-1", "us-west-2"]
}

Access using:
region = tolist(var.allowed_region)[0]

Map(type) - Key-value pairs with string keys Eg: variable "tags" { type = map(string) default = { Environment = "dev" Name = "dev-EC2-instance" } }

Access using:
tags = var.tags

Tuple([type1, type2, ...]) - Ordered collection with specific types for each element. Eg: variable "ingress_values" { type = tuple([number, string, number]) default = [443, "tcp", 443] }

Access using:
from_port = var.ingress_values[0]
ip_protocol = var.ingress_values[1]
to_port = var.ingress_values[2]

Object({key1=type1, key2=type2, ...}) - Structured data with named attributes.
Eg:
variable "config" {
type = object({
region = string,
monitoring = bool,
instance_count = number
})

default = {
region = "us-east-1",
monitoring = true,
instance_count = 1
}
}