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

```hcl
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}"
}