Trait v9::prelude_lib::Deref1.0.0[−][src]

#[lang = "deref"]pub trait Deref {
    type Target: ?Sized;
#[must_use]    pub fn deref(&self) -> &Self::Target;
}

Used for immutable dereferencing operations, like *v.

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

Implementing Deref for smart pointers makes accessing the data behind them convenient, which is why they implement Deref. On the other hand, the rules regarding Deref and DerefMut were designed specifically to accommodate smart pointers. Because of this, Deref 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 Deref is invoked implicitly.

More on Deref coercion

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

  • In immutable contexts, *x (where T is neither a reference nor a raw pointer) is equivalent to *Deref::deref(&x).
  • Values of type &T are coerced to values of type &U
  • T implicitly implements all the (immutable) methods of the type U.

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 accessible by dereferencing the struct.

use std::ops::Deref;

struct DerefExample<T> {
    value: T
}

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

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

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

Associated Types

type Target: ?Sized[src]

The resulting type after dereferencing.

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Required methods

#[must_use]pub fn deref(&self) -> &Self::Target[src]

Dereferences the value.

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Implementations on Foreign Types

impl<T, F> Deref for SyncLazy<T, F> where
    F: FnOnce() -> T, [src]

type Target = T

impl<'_, T> Deref for MutexGuard<'_, T> where
    T: ?Sized, [src]

type Target = T

impl Deref for PathBuf[src]

type Target = Path

impl<'_, T> Deref for RwLockWriteGuard<'_, T> where
    T: ?Sized, [src]

type Target = T

impl Deref for OsString[src]

type Target = OsStr

impl Deref for CString[src]

type Target = CStr

impl<'_, T> Deref for RwLockReadGuard<'_, T> where
    T: ?Sized, [src]

type Target = T

impl<'a> Deref for IoSliceMut<'a>[src]

type Target = [u8]

impl<'a> Deref for IoSlice<'a>[src]

type Target = [u8]

impl<T, F> Deref for Lazy<T, F> where
    F: FnOnce() -> T, [src]

type Target = T

impl<P> Deref for Pin<P> where
    P: Deref, [src]

type Target = <P as Deref>::Target

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

type Target = T

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

type Target = T

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

type Target = T

impl<'_, T> Deref for Ref<'_, T> where
    T: ?Sized, [src]

type Target = T

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

type Target = VaListImpl<'f>

impl<T> Deref for Arc<T> where
    T: ?Sized, [src]

type Target = T

impl Deref for String[src]

type Target = str

impl<T, A> Deref for Box<T, A> where
    T: ?Sized,
    A: Allocator, [src]

type Target = T

impl<T, A> Deref for Vec<T, A> where
    A: Allocator, [src]

type Target = [T]

impl<'_, B> Deref for Cow<'_, B> where
    B: ToOwned + ?Sized, [src]

type Target = B

impl<T> Deref for Rc<T> where
    T: ?Sized, [src]

type Target = T

impl<'_, T> Deref for PeekMut<'_, T> where
    T: Ord, [src]

type Target = T

impl<A> Deref for SmallVec<A> where
    A: Array, [src]

type Target = [<A as Array>::Item]

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Implementors

impl Deref for GuardMut[src]

type Target = dyn Any

impl Deref for GuardRef[src]

type Target = dyn Any

impl<'a> Deref for UniverseRef<'a>[src]

type Target = Universe

impl<'a, T> Deref for MutButRef<'a, T>[src]

type Target = T

impl<T> Deref for KernelArg<T>[src]

type Target = T

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

type Target = T

impl<T> Deref for AssertUnwindSafe<T>1.9.0[src]

type Target = T

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