Rust Programming Tutorials, Guides & Best Practices

struct Color(i32, i32, i32);
let black = Color(0, 0, 0);

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

fn main() {
    let s = String::from("hello");
    let len = calculate_length(&s); // borrow s immutably
    println!("The length of '{}' is {}.", s, len); // s is still valid
}

fn calculate_length(s: &String) -> usize {
    s.len()
}

• Immutable references (&T) allow read-only access.
• Mutable references (&mut T) allow read-write access but are exclusive.
• You cannot have mutable and immutable references to the same data simultaneously.