Trait std::ops::Deref

#[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

The resulting type after dereferencing.

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Required methods

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

Dereferences the value.

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Implementors

impl Deref for CString

type Target = CStr

fn deref(&self) -> &CStr

impl Deref for OsString

type Target = OsStr

fn deref(&self) -> &OsStr

impl Deref for PathBuf

type Target = Path

fn deref(&self) -> &Path

impl Deref for String

type Target = str

pub fn deref(&self) -> &str

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

type Target = B

pub fn deref(&self) -> &B

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

type Target = T

pub fn deref(&self) -> &T

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

type Target = T

pub fn deref(&self) -> &T

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

type Target = T

pub fn deref(&self) -> &T

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

type Target = T

pub fn deref(&self) -> &T

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

type Target = T

pub fn deref(&self) -> &T

impl<'a> Deref for IoSlice<'a>

type Target = [u8]

fn deref(&self) -> &[u8]

impl<'a> Deref for IoSliceMut<'a>

type Target = [u8]

fn deref(&self) -> &[u8]

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

type Target = VaListImpl<'f>

pub fn deref(&self) -> &VaListImpl<'f>

impl<P> Deref for Pin<P> where
    P: Deref, 

type Target = <P as Deref>::Target

pub fn deref(&self) -> &<P as Deref>::Target

impl<T> Deref for ManuallyDrop<T> where
    T: ?Sized, 

type Target = T

pub fn deref(&self) -> &T

impl<T> Deref for AssertUnwindSafe<T>

type Target = T

fn deref(&self) -> &T

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

type Target = T

pub fn deref(&self) -> &T

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

type Target = T

pub fn deref(&self) -> &T

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

type Target = T

pub fn deref(&self) -> &T

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

type Target = [T]

pub fn deref(&self) -> &[T]

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

type Target = T

pub fn deref(&self) -> &T

impl<T, F: FnOnce() -> T> Deref for SyncLazy<T, F>

type Target = T

fn deref(&self) -> &T

impl<T: ?Sized> Deref for MutexGuard<'_, T>

type Target = T

fn deref(&self) -> &T

impl<T: ?Sized> Deref for RwLockReadGuard<'_, T>

type Target = T

fn deref(&self) -> &T

impl<T: ?Sized> Deref for RwLockWriteGuard<'_, T>

type Target = T

fn deref(&self) -> &T

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