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

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

A mutable reference to data in a TrustCell.

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

Implementations

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

Formats the value using the given formatter. Read more

The resulting type after dereferencing.

Dereferences the value.

Mutably dereferences the value.

Executes the destructor for this type. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Performs the conversion.

Performs the conversion.

The alignment of pointer.

The type for initializers.

Initializes a with the given initializer. Read more

Dereferences the given pointer. Read more

Mutably dereferences the given pointer. Read more

Drops the object pointed to by the given pointer. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.