Type constraints in variables in Terraform - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding type constraints in Terraform variables

Which Terraform variable declaration correctly restricts the variable to accept only a list of strings?

A variable "names" { type = string }

B variable "names" { type = map(string) }

C variable "names" { type = any }

D variable "names" { type = list(string) }

💡 Hint

Think about the data structure that holds multiple string values in order.

The list(string) type constraint ensures the variable only accepts a list where each item is a string. Other options either expect different data types or allow any type.

❓ Configuration

intermediate

Identifying invalid type constraint in Terraform variable

Which variable declaration will cause a Terraform configuration error due to an invalid type constraint?

A variable "enabled" { type = bool }

B variable "config" { type = map(any) }

C variable "settings" { type = list[object] }

D variable "count" { type = number }

💡 Hint

Check the syntax for declaring a list of objects in Terraform.

The correct syntax for a list of objects is list(object) with parentheses, not square brackets. Option C uses square brackets which is invalid.

❓ Architecture

advanced

Choosing the correct type constraint for complex variable

You want to define a Terraform variable that accepts a map where each key is a string and each value is an object with two attributes: id (string) and enabled (bool). Which type constraint is correct?

A variable "resources" { type = list(object({ id = string, enabled = bool })) }

B variable "resources" { type = map(object({ id = string, enabled = bool })) }

C variable "resources" { type = map(tuple([string, bool])) }

D variable "resources" { type = object({ id = string, enabled = bool }) }

💡 Hint

Think about the data structure: a map with string keys and object values.

Option B correctly defines a map with string keys and object values having the specified attributes. Option B uses a list instead of a map. Option B uses tuple which does not name attributes. Option B defines a single object, not a map.

❓ security

advanced

Preventing insecure input with type constraints

Which Terraform variable type constraint best prevents users from passing sensitive data as a plain string by enforcing a map with specific keys?

A variable "credentials" { type = object({ username = string, password = string }) }

B variable "credentials" { type = any }

C variable "credentials" { type = string }

D variable "credentials" { type = map(string) }

💡 Hint

Consider how to enforce structure and keys for sensitive data.

Using an object type with named attributes enforces that the variable must include both username and password keys as strings, preventing arbitrary or insecure input formats.

❓ service_behavior

expert

Effect of incorrect type constraint on Terraform plan

Given the variable declaration variable "ports" { type = list(number) }, what will happen if the user provides ["80", "443"] as input during terraform plan?

A Terraform plan will fail with a type mismatch error because strings are provided instead of numbers.

B Terraform plan will succeed and convert strings to numbers automatically.

C Terraform plan will ignore the variable and use default values.

D Terraform plan will succeed but treat the ports as strings.

💡 Hint

Think about how Terraform enforces variable types strictly during planning.

Terraform enforces type constraints strictly. Providing strings where numbers are expected causes a type mismatch error during plan, preventing deployment.