Trait nom::lib::std::ops::DerefMut1.0.0[−][src]

#[lang = "deref_mut"]
pub trait DerefMut: Deref {
    pub fn deref_mut(&mut self) -> &mut Self::Target;
}
[−]

Used for mutable dereferencing operations, like in *v = 1;.

In addition to being used for explicit dereferencing operations with the (unary) * operator in mutable contexts, DerefMut is also used implicitly by the compiler in many circumstances. This mechanism is called ‘Deref coercion’. In immutable contexts, Deref is used.

Implementing DerefMut for smart pointers makes mutating the data behind them convenient, which is why they implement DerefMut. On the other hand, the rules regarding Deref and DerefMut were designed specifically to accommodate smart pointers. Because of this, DerefMut should only be implemented for smart pointers to avoid confusion.

For similar reasons, this trait should never fail. Failure during dereferencing can be extremely confusing when DerefMut is invoked implicitly.

More on Deref coercion

If T implements DerefMut<Target = U>, and x is a value of type T, then:

For more details, visit the chapter in The Rust Programming Language as well as the reference sections on the dereference operator, method resolution and type coercions.

Examples

A struct with a single field which is modifiable by dereferencing the struct.

use std::ops::{Deref, DerefMut};

struct DerefMutExample<T> {
    value: T
}

impl<T> Deref for DerefMutExample<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.value
    }
}

impl<T> DerefMut for DerefMutExample<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.value
    }
}

let mut x = DerefMutExample { value: 'a' };
*x = 'b';
assert_eq!('b', *x);

Required methods

pub fn deref_mut(&mut self) -> &mut Self::Target[src][−]

Mutably dereferences the value.

Implementations on Foreign Types

impl<P> DerefMut for Pin<P> where
    P: DerefMut,
    <P as Deref>::Target: Unpin, [src][−]

impl<'a, 'f> DerefMut for VaList<'a, 'f> where
    'f: 'a, [src][−]

impl<'_, T> DerefMut for RefMut<'_, T> where
    T: ?Sized, [src][−]

Implementors

impl<'_, T> !DerefMut for &'_ T where
    T: ?Sized, [src]

impl<'_, T> DerefMut for &'_ mut T where
    T: ?Sized, [src][+]

impl<T> DerefMut for ManuallyDrop<T> where
    T: ?Sized, 1.20.0[src][+]

impl<T: ?Sized + Pointable> DerefMut for Owned<T>

impl<T> DerefMut for CachePadded<T>

impl<T: ?Sized> DerefMut for ShardedLockWriteGuard<'_, T>

impl<L, R> DerefMut for Either<L, R> where
    L: DerefMut,
    R: DerefMut<Target = L::Target>, 

impl<'a, R: Resources, T: 'a + Copy> DerefMut for Writer<'a, R, T>

impl<P, Container> DerefMut for ImageBuffer<P, Container> where
    P: Pixel + 'static,
    P::Subpixel: 'static,
    Container: Deref<Target = [P::Subpixel]> + DerefMut, 

impl DerefMut for IoVec

impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> DerefMut for MutexGuard<'a, R, T>

impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> DerefMut for MappedMutexGuard<'a, R, T>

impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> DerefMut for RwLockWriteGuard<'a, R, T>

impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> DerefMut for MappedRwLockWriteGuard<'a, R, T>

impl DerefMut for MmapMut

impl DerefMut for UnixReady

impl<T, F: FnOnce() -> T> DerefMut for Lazy<T, F>

impl<T, F: FnOnce() -> T> DerefMut for Lazy<T, F>

impl<T, F, S> DerefMut for ScopeGuard<T, F, S> where
    F: FnOnce(T),
    S: Strategy, 

impl<A: Array> DerefMut for SmallVec<A>

impl DerefMut for Underscore

impl DerefMut for Add

impl DerefMut for And

impl DerefMut for At

impl DerefMut for Bang

impl DerefMut for Caret

impl DerefMut for Colon

impl DerefMut for Comma

impl DerefMut for Div

impl DerefMut for Dollar

impl DerefMut for Dot

impl DerefMut for Eq

impl DerefMut for Gt

impl DerefMut for Lt

impl DerefMut for Or

impl DerefMut for Pound

impl DerefMut for Question

impl DerefMut for Rem

impl DerefMut for Semi

impl DerefMut for Star

impl DerefMut for Sub

impl DerefMut for Tilde