Type constraints in variables in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable that only accepts strings.

Terraform

variable "example_var" {
  type = [1]
}

Drag options to blanks, or click blank then click option'

Abool

Bstring

Cnumber

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'number' instead of 'string' causes errors when assigning text.

Using 'bool' restricts to true/false only.

The string type constraint ensures the variable only accepts string values.

2fill in blank

medium

Complete the code to declare a variable that only accepts a list of strings.

Terraform

variable "example_list" {
  type = [1]
}

Drag options to blanks, or click blank then click option'

Aset(number)

Bmap(string)

Clist(string)

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'map(string)' expects key-value pairs, not a list.

Using 'string' expects a single string, not a list.

The list(string) type constraint ensures the variable accepts a list where each item is a string.

3fill in blank

hard

Fix the error in the variable type declaration to accept a map with string keys and number values.

Terraform

variable "example_map" {
  type = [1]
}

Drag options to blanks, or click blank then click option'

Aobject({key=string})

Bmap(string)

Clist(number)

Dmap(number)

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'map(string)' expects string values, not numbers.

Using 'object' requires a different syntax and is more complex.

The map(number) type constraint allows a map with string keys and number values.

4fill in blank

hard

Fill both blanks to declare a variable that accepts an object with a string 'name' and a number 'age'.

Terraform

variable "person" {
  type = object({
    name = [1],
    age  = [2]
  })
}

Drag options to blanks, or click blank then click option'

Astring

Bnumber

Cbool

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the types for 'name' and 'age' causes errors.

Using 'bool' or 'list' types here is incorrect.

The object type requires specifying each attribute's type. Here, 'name' is a string and 'age' is a number.

5fill in blank

hard

Fill all three blanks to declare a variable that accepts a tuple with a string, a number, and a bool.

Terraform

variable "tuple_var" {
  type = tuple([[1], [2], [3]])
}

Drag options to blanks, or click blank then click option'

Astring

Bnumber

Cbool

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'list' inside tuple is incorrect.

Mixing the order of types causes type errors.

The tuple type defines an ordered list of fixed types: string, number, and bool in this order.

Practice

1. What is the main purpose of using type constraints in Terraform variables?

easy

A. To assign default values to variables

B. To make variables optional

C. To encrypt variable values

D. To ensure variables only accept specific kinds of data

Solution

1. Step 1: Understand variable type constraints

   Type constraints limit what kind of data a variable can accept, like strings or lists.

2. Step 2: Identify the purpose

   This helps catch errors early by preventing wrong data types from being used.

3. Final Answer:

   To ensure variables only accept specific kinds of data -> Option D

4. Quick Check:

   Type constraints = restrict data type [OK]

Hint: Type constraints restrict variable data types [OK]

Common Mistakes:

• Confusing type constraints with default values
• Thinking type constraints make variables optional
• Assuming type constraints encrypt data

2. Which of the following is the correct syntax to declare a variable with a list of strings type constraint in Terraform?

easy

A. variable "names" { type = list(string) }

B. variable "names" { type = "list of strings" }

C. variable "names" { type = [string] }

D. variable "names" { type = string[] }

Solution

1. Step 1: Recall Terraform type syntax

   Terraform uses list(string) to specify a list of strings as a type.

2. Step 2: Compare options

   variable "names" { type = list(string) } uses the correct syntax. Others use invalid or unsupported formats.

3. Final Answer:

   variable "names" { type = list(string) } -> Option A

4. Quick Check:

   List of strings = list(string) [OK]

Hint: Use list(string) for list of strings type [OK]

Common Mistakes:

• Using quotes around type names incorrectly
• Using array syntax like string[] which is invalid in Terraform
• Writing type as a plain string description

3. Given this variable declaration:

variable "ports" {
  type = set(number)
  default = [80, 443, 8080]
}

What will be the type and value of var.ports when accessed in Terraform?

medium

A. A list of numbers: [80, 443, 8080]

B. A set of numbers: {80, 443, 8080}

C. A map with keys 80, 443, 8080

D. A string containing "80,443,8080"

Solution

1. Step 1: Understand the declared type

   The variable type is set(number), which means a set of unique numbers.

2. Step 2: Check the default value

   The default is a list, but Terraform converts it to a set because of the type constraint.

3. Final Answer:

   A set of numbers: {80, 443, 8080} -> Option B

4. Quick Check:

   Type set(number) = set of numbers [OK]

Hint: set(number) converts list to unique number set [OK]

Common Mistakes:

• Confusing set with list type
• Expecting a map instead of a set
• Thinking default list stays a list despite type

4. Identify the error in this variable declaration:

variable "config" {
  type = map(string)
  default = ["a", "b", "c"]
}

medium

A. Default values must be numbers

B. Type map(string) is invalid syntax

C. Default value is a list, but type expects a map

D. Variable name cannot be "config"

Solution

1. Step 1: Analyze the type constraint

   The type map(string) expects a map with string values, like { key = "value" }.

2. Step 2: Check the default value

   The default is a list, which does not match the map type.

3. Final Answer:

   Default value is a list, but type expects a map -> Option C

4. Quick Check:

   Type map(string) needs map, not list [OK]

Hint: Match default value type to variable type [OK]

Common Mistakes:

• Using list as default for map type
• Thinking map(string) is invalid syntax
• Believing variable names are restricted

5. You want a variable that accepts either a string or a list of strings. Which type constraint correctly allows this in Terraform?

hard

A. type = string | list(string)

B. type = any

C. type = object({ string_or_list = string })

D. type = string, list(string)

Solution

1. Step 1: Understand union types in Terraform

   Terraform supports union types using the pipe symbol | to allow multiple types.

2. Step 2: Identify correct syntax

   type = string | list(string) uses string | list(string), which means the variable can be either a string or a list of strings.

3. Step 3: Check other options

   type = any allows any type, which is too broad. type = object({ string_or_list = string }) defines an object, not a union. type = string, list(string) is invalid syntax.

4. Final Answer:

   type = string | list(string) -> Option A

5. Quick Check:

   Union type uses | to combine types [OK]

Hint: Use | to combine types for union constraints [OK]

Common Mistakes:

• Using commas instead of | for union types
• Choosing any type instead of specific union
• Confusing object type with union type