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Pointers

Box: smart pointer​

All values in Rust are allocated on stack by default. Values wrapped by Box can be allocated on heap, Box<T> is a smart pointer to the value of type T. When a box goes out of scope, its destructor is called, the inner object is destroyed, and the memory on the heap is freed.

Cheatsheet​

let x = Box::new<value>;
let value: Type = *x;
fn return_trait() -> Box<dyn TraitType> { todo!() }

Questions​

When to use smart pointers

Ref

  • You want to own a dynamically sized object, like Box<dyn SomeTrait>
  • You want to leak an object into 'static lifetime
  • You want to produce an ffi pointer
  • You want to make recursive types