Packages

Using and creating Cargo packages.

Intermediate⏱️ 35 min📚 Prerequisites: 1

Packages

A package consists of one or more crates that together provide a functionality.

Package Structure

my_project/
├── Cargo.toml
└── src/
    └── main.rs

Binary Crate


RUST
// src/main.rs
fn main() {
    println!("Hello, world!");
}

Library Crate


RUST
// src/lib.rs
pub fn add(left: u64, right: u64) -> u64 {
    left + right
}

Cargo.toml


TOML
[package]
name = "my_project"
version = "0.1.0"
edition = "2021"

[dependencies]

Adding Dependencies


TOML
[dependencies]
serde = "1.0"
rand = "0.8"

Workspace


TOML
[workspace]
members = [
    "adder",
    "add_one",
]

Public API


RUST
// src/lib.rs
pub mod front_of_house {
    pub mod hosting {
        pub fn add_to_waitlist() {}
    }
}

pub use crate::front_of_house::hosting;

Code Examples

Cargo.toml

Package configuration

RUST

# Cargo.toml
[package]
name = "my_project"
version = "0.1.0"
edition = "2021"
[dependencies]
# Dependencies go here

Explanation:

The Cargo.toml file contains package metadata and dependencies. name, version, and edition are required fields.

Binary Crate

Creating an executable program

RUST

fn main() {
    println!("Hello from binary crate!");
    let result = my_lib::add(5, 3);
    println!("5 + 3 = {}", result);
}
pub mod my_lib {
    pub fn add(x: i32, y: i32) -> i32 {
        x + y
    }
}

Explanation:

A binary crate is an executable program. main.rs contains the main() function. lib.rs defines a library crate.

Dependencies

Using external crates

RUST

# Cargo.toml
[dependencies]
rand = "0.8"
use rand::Rng;
fn main() {
    let mut rng = rand::thread_rng();
    let number: u32 = rng.gen_range(1..=100);
    println!("Random number: {}", number);
}

Explanation:

In the Cargo.toml [dependencies] section, we can add external crates. cargo build automatically downloads and compiles them.

Exercises

Creating a Package

Create a new Cargo project!

Easy

Starter Code:

RUST

# Cargo.toml
# Write the package configuration
# src/main.rs
# Write the main function