[][src]Struct shred::cell::RefMut

pub struct RefMut<'a, T: ?Sized + 'a> { /* fields omitted */ }

A mutable reference to data in a TrustCell.

Access the value via std::ops::DerefMut (e.g. *val)

Methods

impl<'a, T: ?Sized> RefMut<'a, T>[src]

pub fn map<U, F>(self, f: F) -> RefMut<'a, U> where
    F: FnOnce(&mut T) -> &mut U,
    U: ?Sized
[src]

Makes a new RefMut for a component of the borrowed data which preserves the existing borrow.

The TrustCell is already mutably borrowed, so this cannot fail.

This is an associated function that needs to be used as RefMut::map(...). A method would interfere with methods of the same name on the contents of a RefMut used through DerefMut. Further this preserves the borrow of the value and hence does the proper cleanup when it's dropped.

Examples

This can also be used to avoid pointer indirection when a boxed item is stored in the TrustCell.

use shred::cell::{RefMut, TrustCell};

let cb = TrustCell::new(Box::new(5));

// Borrowing the cell causes the `RefMut` to store a reference to the `Box`, which is a
// pointer to the value on the heap, and not a reference directly to the value.
let boxed_ref: RefMut<'_, Box<usize>> = cb.borrow_mut();
assert_eq!(**boxed_ref, 5); // Notice the double deref to get the actual value.

// By using `map` we can let `RefMut` store a reference directly to the value on the heap.
let pure_ref: RefMut<'_, usize> = RefMut::map(boxed_ref, Box::as_mut);

assert_eq!(*pure_ref, 5);

We can also use map to get a reference to a sub-part of the borrowed value.


let c = TrustCell::new((5, 'b'));

let b1: RefMut<'_, (u32, char)> = c.borrow_mut();
let b2: RefMut<'_, u32> = RefMut::map(b1, |t| &mut t.0);
assert_eq!(*b2, 5);

Trait Implementations

impl<'a, T: ?Sized> Drop for RefMut<'a, T>[src]

impl<'a, T: ?Sized> Deref for RefMut<'a, T>[src]

type Target = T

The resulting type after dereferencing.

impl<'a, T: ?Sized> DerefMut for RefMut<'a, T>[src]

impl<'a, T: Debug + ?Sized + 'a> Debug for RefMut<'a, T>[src]

Auto Trait Implementations

impl<'a, T: ?Sized> Unpin for RefMut<'a, T>

impl<'a, T: ?Sized> Sync for RefMut<'a, T> where
    T: Sync

impl<'a, T: ?Sized> Send for RefMut<'a, T> where
    T: Send

impl<'a, T> !UnwindSafe for RefMut<'a, T>

impl<'a, T: ?Sized> RefUnwindSafe for RefMut<'a, T> where
    T: RefUnwindSafe

Blanket Implementations

impl<T> From<T> for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<T> Any for T where
    T: Any
[src]