Struct Ref

pub struct Ref<'b, T: ?Sized + 'b> { /* private fields */ }

Wraps a borrowed reference to a value in a RefCell box. A wrapper type for an immutably borrowed value from a RefCell<T>.

See the module-level documentation for more.

Implementations

impl<'b, T: ?Sized + 'b> Ref<'b, T>

pub fn map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U>

where F: FnOnce(&T) -> &U,

Makes a new Ref for a component of the borrowed data.

The RefCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::map(...). A method would interfere with methods of the same name on the contents of a RefCell used through Deref.

Examples

use std::cell::{RefCell, Ref};

let c = RefCell::new((5, 'b'));
let b1: Ref<'_, (u32, char)> = c.borrow();
let b2: Ref<'_, u32> = Ref::map(b1, |t| &t.0);
assert_eq!(*b2, 5)

Trait Implementations

impl<'b, T: ?Sized> Deref for Ref<'b, T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.