Struct AccessCell 

pub struct AccessCell<'a, 'b, T> { /* private fields */ }

AccessCell allows feather to track when a value passed into a function has actually been changed, by tracking if a mutable borrow has been requested. Like std::cell::RefCell, it implements std::borrow::Borrow and std::borrow::BorrowMut, but also implements the std::ops::Deref and std::ops::DerefMut operators so it can be used more like a smart pointer.

Generally speaking, this type should never be constructed - it is used at Feather’s API boundaries where appropriate.

Examples

use feather_ui::AccessCell;

struct FooBar {
  i: i32,
}

fn change(change: bool, mut v: AccessCell<FooBar>) {
    if change {
        // FooBar only marked as changed once this mutable access happens
        v.i = 4;
    }
}

Future-proofing

Currently, AccessCell does not attempt to determine if the new value is actually different than what was previously stored, because this would be a very expensive comparison. However, in the future, a specialization of AccessCell for Persistent data structures that only marks the value as changed if it is actually different when the AccessCell is dropped might be implemented. As a result, you should assume that AccessCell implements Drop even if it technically doesn’t right now.

Trait Implementations

impl<'a, 'b, T> Borrow<T> for AccessCell<'a, 'b, T>

fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<'a, 'b, T> BorrowMut<T> for AccessCell<'a, 'b, T>

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value.

impl<'a, 'b, T> Deref for AccessCell<'a, 'b, T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<'a, 'b, T> DerefMut for AccessCell<'a, 'b, T>

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.