Terraform Variables

Type Constraints

Primitive Types:

string	A sequence of Unicode characters.
number	A numeric value
bool	Either true or False

Constructors:

A. Collection Types:

list	A sequence of values identified by consective whole numbers starting with zero.
map	A collection of values where each is identified by a string label.
set	A collection of UNIQUE values that do not have any secondary identifiers or ordering

B. Structural Types

Object	A collection of names attributes that each have their own type
Tuple	A sequence of elements identified by consecutive whoe numbers starting with zero, where each element has its own type

Differences

| Set | Similar to lists and tuples, but does not contains duplicate values and ordering of elements is lost | | List | Lists are mutable, which means you can add, remove, or modify elements after the list is created | | Tuples | Tuples are immutable, which means they cannot be changed once created |

Declaration and Examples:

String

# Declaration
variable "city" {
  type = string
}

# Example
city = "california"

# Output
output "string" {
    value = var.city
}

Number

# Declaration
variable "age" {
  type = number
}

# Example
age = 32

# Output
output "number" {
    value = var.age
}

Boolean

# Declaration
variable "flag" {
  type = bool
}

# Example
flag = true

# Output
output "bool" {
    value = var.flag
}

List

# Declaration
variable userlist {
    type = list(string)
}

# Example
userlist = ["john", "jane", "mary"]

# Output
output "list" {
    value = [for user in var.userlist: user]
}

Map

# Declaration
variable userdetails {
    type = map()
}

# Example
userdetails = {
    john = 32
    jane = 31
    mary = 30
}

# Output
output "map" {
    value = [for user in var.userdetails: user]
}

output "map_filtered" {
    value = [var.userdetails["john"]]
}

Set

# Declaration
variable "usernames" {
  type = set(string)
}

# Example
# Set Example
usernames = [
    "john",
    "jane",
]

# Output
output "set" {
    value = [for user in var.usernames: user]
}

Object

# Declaration
variable user = Object({
    name = string
    age = number
})

# Example
user1 = ({
    name = "John"
    age = 32
})

# Output
output "object" {
    value = "${var.objectuserdetails}"
}

Tuple

# Declaration
variable "tupleuserdetails" {
  type = tuple([string, number, bool])
}

# Example
tupleuserdetails = [ "john", 32 , true ]

# Output
output "tuple" {
    value = "${var.tupleuserdetails}"
}