4.1 What is Ownership?

Ownership

• Most unique feature of rust which makes its memory safety guarantees, without any use of garbage collector.

• Way to manage memory

• Why should we manage memory?

  

  Cannot optimize memory → Slow

  Cannot predict memory collectors behavior → Unpredictable runtime

  Invalid memory accessby programmer can be possible → Error prone

  Memory writing is much slower → Slower write time

  Ownership model : Slower than manual memory management

Memory - Stack vs Heap

Ownership Rules

1. Each value in Rust has a variable that’s called its owner.
2. There can only be one owner at a time.
3. When the owner goes out of scope, the value will be dropped.

Move Ownership

fn main() {
    let x = 5;
    let y = x; //copy

    let s1 = String::from("hello");
    let s2 = s1; //move ownership
}

Make new heap allocation?

Expansive!

Especially when the data on the heap were large.

s2 = s1 could be very expensive in terms of runtime performance.

(allocation)

Make copy of pointers?