Rust Ownership: The Mental Model That Makes It Click

Key Insights

• Think of ownership as a compile-time garbage collector that runs at zero cost
• Most ownership errors come from trying to use values after moving them
• Clone is not a code smell — sometimes explicit copies are the right choice

The Core Rules

1. Each value has exactly one owner
2. When the owner goes out of scope, the value is dropped
3. You can transfer ownership (move) or borrow (reference)

fn main() {
    let name = String::from("hello");
    let greeting = format!("Hi, {name}"); // name is borrowed here, not moved
    println!("{greeting}");
    println!("{name}"); // still valid
}

When to Clone

If you’re fighting the borrow checker and the data is small, just clone it:

let config = load_config();
let handler = move || {
    process(config.clone()) // explicit copy, no lifetime issues
};

References vs Ownership

Use &T when you just need to read. Use &mut T when you need to modify. Take ownership (T) only when you need to store or consume the value.