What are the typical use cases that require taking ownership of self?

Question

In the Rust book Method Syntax chapter, there's an example of taking ownership of self:

struct Circle {
    x: f64,
    y: f64,
    radius: f64,
}

impl Circle {
    fn reference(&self) {
        println!("taking self by reference!");
    }

   fn mutable_reference(&mut self) {
       println!("taking self by mutable reference!");
   }

   fn takes_ownership(self) {
      println!("taking ownership of self!");
   }
}

What are the typical use cases that require taking ownership of self? Is it only when self is a value on the stack (where it will be copied)?

Answer 1

Taking ownership makes sense when the object is invalidated by the method. Imagine a method Iterator.drop(u32), implemented as returning a new object instead of modifying the existing one. Calling additional methods on the original iterator would lead to inconsistencies.

Other examples for such invalidation would be different sorts of wrappers.