Ownership in Rust

Ownership is Rust’s most unique feature and enables memory safety without garbage collection.

Ownership Rules

Each value has an owner
Only one owner at a time
Value is dropped when owner goes out of scope

Move Semantics

rust

fn main() {
    let s1 = String::from("hello");
    let s2 = s1;  // s1 is moved to s2
    
    // println!("{}", s1);  // Error! s1 is no longer valid
    println!("{}", s2);    // OK
}

Clone

rust

fn main() {
    let s1 = String::from("hello");
    let s2 = s1.clone();  // Deep copy
    
    println!("s1 = {}, s2 = {}", s1, s2);  // Both valid
}

References and Borrowing

rust

fn main() {
    let s = String::from("hello");
    let len = calculate_length(&s);  // Borrow s
    println!("Length of '{}' is {}", s, len);  // s still valid
}

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

Mutable References

rust

fn main() {
    let mut s = String::from("hello");
    change(&mut s);
    println!("{}", s);  // "hello, world"
}

fn change(s: &mut String) {
    s.push_str(", world");
}