Struct UncheckedRefMut

Source

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

Expand description

A wrapper type for a mutably borrowed value from a RefCell<T>.

See the module-level documentation for more.

Implementations§

Source §

impl<'b, T: ?Sized> UncheckedRefMut<'b, T>

Source

pub fn map<U: ?Sized, F>( orig: UncheckedRefMut<'b, T>, f: F, ) -> UncheckedRefMut<'b, U>
where F: FnOnce(&mut T) -> &mut U,

Makes a new UncheckedRefMut for a component of the borrowed data, e.g., an enum variant.

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

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

§Examples

use unchecked_refcell::{UncheckedRefCell, UncheckedRefMut};

let c = UncheckedRefCell::new((5, 'b'));
{
    let b1: UncheckedRefMut<'_, (u32, char)> = c.borrow_mut();
    let mut b2: UncheckedRefMut<'_, u32> = UncheckedRefMut::map(b1, |t| &mut t.0);
    assert_eq!(*b2, 5);
    *b2 = 42;
}
assert_eq!(*c.borrow(), (42, 'b'));

Source

pub fn filter_map<U: ?Sized, F>( orig: UncheckedRefMut<'b, T>, f: F, ) -> Result<UncheckedRefMut<'b, U>, Self>
where F: FnOnce(&mut T) -> Option<&mut U>,

Makes a new UncheckedRefMut for an optional component of the borrowed data. The original guard is returned as an Err(..) if the closure returns None.

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

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

§Examples

use unchecked_refcell::{UncheckedRefCell, UncheckedRefMut};

let c = UncheckedRefCell::new(vec![1, 2, 3]);

{
    let b1: UncheckedRefMut<'_, Vec<u32>> = c.borrow_mut();
    let mut b2: Result<UncheckedRefMut<'_, u32>, _> = UncheckedRefMut::filter_map(b1, |v| v.get_mut(1));

    if let Ok(mut b2) = b2 {
        *b2 += 2;
    }
}

assert_eq!(*c.borrow(), vec![1, 4, 3]);

Source

pub fn try_map<U: ?Sized, E>( orig: UncheckedRefMut<'b, T>, f: impl FnOnce(&mut T) -> Result<&mut U, E>, ) -> Result<UncheckedRefMut<'b, U>, (Self, E)>

Tries to makes a new UncheckedRefMut for a component of the borrowed data. On failure, the original guard is returned alongside with the error returned by the closure.

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

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

§Examples

use unchecked_refcell::{UncheckedRefCell, UncheckedRefMut};
use std::str::{from_utf8_mut, Utf8Error};

let c = UncheckedRefCell::new(vec![0x68, 0x65, 0x6C, 0x6C, 0x6F]);
{
    let b1: UncheckedRefMut<'_, Vec<u8>> = c.borrow_mut();
    let b2: Result<UncheckedRefMut<'_, str>, _> = UncheckedRefMut::try_map(b1, |v| from_utf8_mut(v));
    let mut b2 = b2.unwrap();
    assert_eq!(&*b2, "hello");
    b2.make_ascii_uppercase();
}
assert_eq!(*c.borrow(), "HELLO".as_bytes());

let c = UncheckedRefCell::new(vec![0xFF]);
let b1: UncheckedRefMut<'_, Vec<u8>> = c.borrow_mut();
let b2: Result<_, (UncheckedRefMut<'_, Vec<u8>>, Utf8Error)> = UncheckedRefMut::try_map(b1, |v| from_utf8_mut(v));
let (b3, e) = b2.unwrap_err();
assert_eq!(*b3, vec![0xFF]);
assert_eq!(e.valid_up_to(), 0);

Source

pub fn map_split<U: ?Sized, V: ?Sized, F>( orig: UncheckedRefMut<'b, T>, f: F, ) -> (UncheckedRefMut<'b, U>, UncheckedRefMut<'b, V>)
where F: FnOnce(&mut T) -> (&mut U, &mut V),

Splits a UncheckedRefMut into multiple UncheckedRefMuts for different components of the borrowed data.

The underlying RefCell will remain mutably borrowed until both returned UncheckedRefMuts go out of scope.

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

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

§Examples

use unchecked_refcell::{UncheckedRefCell, UncheckedRefMut};

let cell = UncheckedRefCell::new([1, 2, 3, 4]);
let borrow = cell.borrow_mut();
let (mut begin, mut end) = UncheckedRefMut::map_split(borrow, |slice| slice.split_at_mut(2));
assert_eq!(*begin, [1, 2]);
assert_eq!(*end, [3, 4]);
begin.copy_from_slice(&[4, 3]);
end.copy_from_slice(&[2, 1]);

Source

pub fn leak(orig: UncheckedRefMut<'b, T>) -> &'b mut T

Converts into a mutable reference to the underlying data.

The underlying RefCell can not be borrowed from again and will always appear already mutably borrowed, making the returned reference the only to the interior.

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

§Examples

use unchecked_refcell::{UncheckedRefCell, UncheckedRefMut};
let cell = UncheckedRefCell::new(0);

let value = UncheckedRefMut::leak(cell.borrow_mut());
assert_eq!(*value, 0);
*value = 1;

assert!(cell.try_borrow_mut().is_err());