Using external crates in Rust - Mini Project: Build & Apply

Using external crates

📖 Scenario: You want to use a popular external crate called rand to generate random numbers in your Rust program. This is common when you need random values for games, simulations, or testing.

🎯 Goal: Learn how to add an external crate to your Rust project and use it to generate a random number between 1 and 10.

📋 What You'll Learn

Create a new Rust project with Cargo

Add the rand crate as a dependency in Cargo.toml

Import the rand crate in your main.rs

Generate and print a random number between 1 and 10

💡 Why This Matters

🌍 Real World

Random numbers are used in games, simulations, and testing to add unpredictability and variety.

💼 Career

Knowing how to use external crates is essential for Rust developers to reuse code and add functionality quickly.

1

Create a new Rust project

Use the command cargo new random_number in your terminal to create a new Rust project folder called random_number. Then open the main.rs file inside the src folder. Write a main function that prints "Hello, world!".

Rust

fn main() {
    // Your code here
}

Hint

Use println!("Hello, world!"); inside the main function.

2

Add the rand crate to Cargo.toml

Open the Cargo.toml file in your project root. Add the line rand = "0.8" under the [dependencies] section to include the rand crate version 0.8.

Rust

fn main() {
    println!("Hello, world!");
}

// Add 'rand = "0.8"' under [dependencies] in Cargo.toml

Hint

Find the [dependencies] section in Cargo.toml and add rand = "0.8" below it.

3

Import rand and generate a random number

In main.rs, add use rand::Rng; at the top. Inside main, create a variable random_number that uses rand::thread_rng().gen_range(1..=10) to generate a random number between 1 and 10.

Rust

use rand::Rng;

fn main() {
    // Your code here
}

Hint

Import rand::Rng and use rand::thread_rng().gen_range(1..=10) to get a random number.

4

Print the random number

Add a println! statement to print the text "Random number: {random_number}" where {random_number} is the variable you created.

Rust

use rand::Rng;

fn main() {
    let random_number = rand::thread_rng().gen_range(1..=10);
    // Your code here
}

Hint

Use println!("Random number: {}", random_number); to show the number.