Match with enums in Rust - Mini Project: Build & Apply

Match with enums

📖 Scenario: You are building a simple program to identify the type of a vehicle based on an enum. This is like sorting different types of vehicles into categories, such as cars, bikes, or trucks.

🎯 Goal: Create an enum called Vehicle with three variants: Car, Bike, and Truck. Then use a match statement to print a message describing the vehicle type.

📋 What You'll Learn

Create an enum named Vehicle with variants Car, Bike, and Truck

Create a variable called my_vehicle and assign it the value Vehicle::Bike

Use a match statement on my_vehicle with arms for each variant

Print a message for each variant exactly as: "It's a car!", "It's a bike!", or "It's a truck!"

💡 Why This Matters

🌍 Real World

Enums and match statements are used in many programs to handle different states or types clearly and safely, like handling different user actions or device types.

💼 Career

Understanding enums and pattern matching is essential for Rust programming jobs, especially in system programming, game development, and backend services.

1

Create the Vehicle enum

Create an enum called Vehicle with three variants: Car, Bike, and Truck.

Rust

# Your code here

Hint

Use the enum keyword followed by the name Vehicle. Inside curly braces, list the variants separated by commas.

2

Create a variable with a Vehicle value

Create a variable called my_vehicle and assign it the value Vehicle::Bike.

Rust

enum Vehicle {
    Car,
    Bike,
    Truck,
}

# Your code here

Hint

Use let to create the variable and assign Vehicle::Bike to it.

3

Use match to check the vehicle type

Use a match statement on my_vehicle with arms for each variant: Car, Bike, and Truck. For each arm, write a comment describing the vehicle type.

Rust

enum Vehicle {
    Car,
    Bike,
    Truck,
}

let my_vehicle = Vehicle::Bike;

match my_vehicle {
    // Your code here
}

Hint

Use match my_vehicle { Vehicle::Car => { }, Vehicle::Bike => { }, Vehicle::Truck => { } }.

4

Print messages for each vehicle type

Inside each match arm, use println! to print exactly: "It's a car!", "It's a bike!", or "It's a truck!" respectively.

Rust

enum Vehicle {
    Car,
    Bike,
    Truck,
}

let my_vehicle = Vehicle::Bike;

match my_vehicle {
    Vehicle::Car => {
        // Print message here
    },
    Vehicle::Bike => {
        // Print message here
    },
    Vehicle::Truck => {
        // Print message here
    },
}

Hint

Use println!("It's a bike!"); inside the Vehicle::Bike arm, and similar for others.

Practice

1.

What does the match statement do when used with enums in Rust?

easy

A. It checks the enum variant and runs the matching code block.

B. It converts the enum into a string automatically.

C. It creates a new enum variant.

D. It deletes the enum variant from memory.

Solution

1. Step 1: Understand the purpose of match with enums

   The match statement compares the enum value against each variant.

2. Step 2: Identify what happens on a match

   When a variant matches, the corresponding code block runs.

3. Final Answer:

   It checks the enum variant and runs the matching code block. -> Option A

4. Quick Check:

   Match runs code by enum variant [OK]

Hint: Match arms correspond to enum variants directly [OK]

Common Mistakes:

• Thinking match converts enums to strings
• Assuming match creates or deletes variants
• Confusing match with if-else statements

2.

Which of the following is the correct syntax to match an enum Color with variants Red, Green, and Blue?

enum Color { Red, Green, Blue }

easy

A. match color { Color.Red => {}, Color.Green => {}, Color.Blue => {} }

B. match color { Red => {}, Green => {}, Blue => {} }

C. match color { Color::Red => {}, Color::Green => {}, Color::Blue => {} }

D. match color { 'Red' => {}, 'Green' => {}, 'Blue' => {} }

Solution

1. Step 1: Recall enum variant syntax in match

   Enum variants must be prefixed with the enum name and double colon, like Color::Red.

2. Step 2: Check each option's syntax

   Only match color { Color::Red => {}, Color::Green => {}, Color::Blue => {} } uses the correct Color::Variant syntax.

3. Final Answer:

   match color { Color::Red => {}, Color::Green => {}, Color::Blue => {} } -> Option C

4. Quick Check:

   Enum variants use EnumName::Variant [OK]

Hint: Use EnumName::Variant in match arms [OK]

Common Mistakes:

• Omitting enum name prefix
• Using dot instead of double colon
• Using strings instead of variants

3.

What will be the output of this Rust code?

enum Direction { North, South, East, West }

fn main() {
    let dir = Direction::East;
    let message = match dir {
        Direction::North => "Going up",
        Direction::South => "Going down",
        Direction::East => "Going right",
        Direction::West => "Going left",
    };
    println!("{}", message);
}

medium

A. Going right

B. Going up

C. Going left

D. Going down

Solution

1. Step 1: Identify the enum variant assigned

   The variable dir is set to Direction::East.

2. Step 2: Match dir to the correct message

   The match arm for Direction::East returns "Going right".

3. Final Answer:

   Going right -> Option A

4. Quick Check:

   Direction::East matches "Going right" [OK]

Hint: Match returns value for the exact enum variant [OK]

Common Mistakes:

• Mixing up enum variants and their messages
• Forgetting to use EnumName::Variant in match
• Assuming default or fallback arm runs

4.

Find the error in this Rust code snippet using match with enums:

enum Status { Success, Failure }

fn check(status: Status) {
    match status {
        Status::Success => println!("Success"),
        // Missing Failure arm
    }
}

medium

A. Missing semicolon after println! macro

B. Function check should return a value

C. Incorrect enum variant syntax

D. Missing match arm for Status::Failure

Solution

1. Step 1: Check completeness of match arms

   The match statement covers Status::Success but misses Status::Failure.

2. Step 2: Understand Rust's exhaustiveness requirement

   Rust requires all enum variants to be matched or a catch-all arm (_) to avoid compile errors.

3. Final Answer:

   Missing match arm for Status::Failure -> Option D

4. Quick Check:

   All enum variants must be matched [OK]

Hint: Match must cover all enum variants or use _ arm [OK]

Common Mistakes:

• Leaving out enum variants in match arms
• Assuming partial match compiles
• Confusing semicolon placement with match completeness

5.

Given this enum with data:

enum Message {
    Quit,
    Move { x: i32, y: i32 },
    Write(String),
    ChangeColor(i32, i32, i32),
}

Which match arm correctly extracts the x and y values from Message::Move?

hard

A. Message::Move(x, y) => println!("x: {}, y: {}", x, y),

B. Message::Move { x, y } => println!("x: {}, y: {}", x, y),

C. Message::Move(x: x, y: y) => println!("x: {}, y: {}", x, y),

D. Message::Move(x: x, y) => println!("x: {}, y: {}", x, y),

Solution

1. Step 1: Identify the enum variant with named fields

   Move uses named fields { x: i32, y: i32 }.

2. Step 2: Match syntax for named fields

   Use Message::Move { x, y } to destructure named fields directly.

3. Final Answer:

   Message::Move { x, y } => println!("x: {}, y: {}", x, y), -> Option B

4. Quick Check:

   Named fields use braces and field names [OK]

Hint: Use braces and field names to destructure named fields [OK]

Common Mistakes:

• Using tuple pattern for struct-like variant
• Mixing colon syntax incorrectly
• Omitting braces for named fields