Struct GcCellRefMut

pub struct GcCellRefMut<'a, T: Trace + ?Sized + 'static, U: ?Sized = T> { /* private fields */ }

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

Implementations

impl<'a, T: Trace + ?Sized, U: ?Sized> GcCellRefMut<'a, T, U>

pub fn map<V, F>(orig: Self, f: F) -> GcCellRefMut<'a, T, V>

where V: ?Sized, F: FnOnce(&mut U) -> &mut V,

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

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

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

Examples

use gc::{GcCell, GcCellRefMut};

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

pub fn filter_map<V, F>( orig: Self, f: F, ) -> Result<GcCellRefMut<'a, T, V>, Self>

where V: ?Sized, F: FnOnce(&mut U) -> Option<&mut V>,

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

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

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

Examples

use gc::{GcCell, GcCellRefMut};

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

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

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

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

Trait Implementations

impl<'a, T: Trace + ?Sized, U: Debug + ?Sized> Debug for GcCellRefMut<'a, T, U>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a, T: Trace + ?Sized, U: ?Sized> Deref for GcCellRefMut<'a, T, U>

type Target = U

The resulting type after dereferencing.

fn deref(&self) -> &U

Dereferences the value.

impl<'a, T: Trace + ?Sized, U: ?Sized> DerefMut for GcCellRefMut<'a, T, U>

fn deref_mut(&mut self) -> &mut U

Mutably dereferences the value.

impl<'a, T: Trace + ?Sized, U: Display + ?Sized> Display for GcCellRefMut<'a, T, U>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a, T: Trace + ?Sized, U: ?Sized> Drop for GcCellRefMut<'a, T, U>

fn drop(&mut self)

Executes the destructor for this type.