Ownership

The core rules

• Each value has one owner
• Only one owner at a time
• When the owner goes out of scope, the value is dropped

Move on assignment

Assigning a String moves ownership; the old name cannot be used.

let a = String::from("hello");
let b = a;
// println!("{a}"); // error: a was moved
println!("{b}");

Clone when you need a copy

clone deep-copies heap data so both names are valid.

let a = String::from("hello");
let b = a.clone();
println!("{a} {b}");

Copy types

Small stack types like integers implement Copy and duplicate automatically.

let x = 5;
let y = x;
println!("{x} {y}");