Ownership

The variable responsible for a value, when it goes out of scope, the value is freed

Always, every value has exactly one

let name = String::from("Alice");
// name is the owner of "Alice"

Transferring ownership to a new variable, the original can no longer be used

When passing a String or Vec to a function

let s1 = String::from("hi");
let s2 = s1; // s1 no longer valid

Duplicating a value so both the original and the new variable stay valid

Integers, booleans, floats, they copy automatically

let x = 5;
let y = x; // both x and y are valid

An explicit full copy of a heap-allocated value

s1.clone(), use when you need two separate values

let s1 = String::from("hello");
let s2 = s1.clone();

When a value goes out of scope and its memory is freed

Happens automatically at the } that closes the scope

{ let s = String::from("bye"); }
// s is dropped here automatically

Fast, fixed-size memory; last in, first out

Primitives like i32, bool, char live here; freed automatically

let x: i32 = 5;
let b: bool = true;

Flexible memory for data that can grow; the variable holds a pointer to it

String, Vec, heap-stored; requires ownership tracking to know when to free

let s = String::from("hello");
let v: Vec<i32> = vec![1, 2];

The text of a String lives on the heap, not the stack

Every String::from(...) or .to_string() causes a heap allocation

let s = String::from("hi");
let s2 = "hello".to_string();