1.0.0[−][src]Trait std::ops::Deref
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
on non-pointer types 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 typeU
.
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);Run
Associated Types
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impl Deref for CString
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impl Deref for OsString
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impl Deref for PathBuf
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impl Deref for String
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impl<'_, B> Deref for Cow<'_, B> where
B: ToOwned + ?Sized,
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B: ToOwned + ?Sized,
impl<'_, T> Deref for &'_ T where
T: ?Sized,
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T: ?Sized,
impl<'_, T> Deref for &'_ mut T where
T: ?Sized,
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T: ?Sized,
impl<'_, T> Deref for Ref<'_, T> where
T: ?Sized,
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T: ?Sized,
impl<'_, T> Deref for RefMut<'_, T> where
T: ?Sized,
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T: ?Sized,
impl<'_, T> Deref for PeekMut<'_, T> where
T: Ord,
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T: Ord,
impl<'_, T: ?Sized> Deref for MutexGuard<'_, T>
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impl<'_, T: ?Sized> Deref for RwLockReadGuard<'_, T>
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impl<'_, T: ?Sized> Deref for RwLockWriteGuard<'_, T>
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impl<'a> Deref for IoSlice<'a>
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impl<'a> Deref for IoSliceMut<'a>
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impl<P> Deref for Pin<P> where
P: Deref,
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P: Deref,
impl<T> Deref for Box<T> where
T: ?Sized,
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T: ?Sized,
impl<T> Deref for ManuallyDrop<T> where
T: ?Sized,
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T: ?Sized,
impl<T> Deref for AssertUnwindSafe<T>
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impl<T> Deref for Rc<T> where
T: ?Sized,
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T: ?Sized,
impl<T> Deref for Arc<T> where
T: ?Sized,
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T: ?Sized,