Trait nom::lib::std::ops::Deref 1.0.0
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#[lang = "deref"]pub trait Deref { type Target: ?Sized; 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
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) -> &T { &self.value } } let x = DerefExample { value: 'a' }; assert_eq!('a', *x);
Associated Types
Required Methods
Implementations on Foreign Types
impl<'mutex, T> Deref for MutexGuard<'mutex, T> where
T: ?Sized,
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T: ?Sized,
impl Deref for CString
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impl<'rwlock, T> Deref for RwLockWriteGuard<'rwlock, T> where
T: ?Sized,
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T: ?Sized,
impl<T> Deref for AssertUnwindSafe<T>
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impl Deref for OsString
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impl<'rwlock, T> Deref for RwLockReadGuard<'rwlock, T> where
T: ?Sized,
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T: ?Sized,
impl Deref for PathBuf
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impl<'b, T> Deref for Ref<'b, T> where
T: ?Sized,
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T: ?Sized,
impl<'b, T> Deref for RefMut<'b, T> where
T: ?Sized,
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T: ?Sized,
impl<'a, T> Deref for &'a mut T where
T: ?Sized,
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T: ?Sized,
impl<'a, T> Deref for &'a T where
T: ?Sized,
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T: ?Sized,
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,
impl<'a, B> Deref for Cow<'a, B> where
B: ToOwned + ?Sized,
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B: ToOwned + ?Sized,
Implementors
impl<T> Deref for ManuallyDrop<T> type Target = T;
impl<T> Deref for Box<T> where
T: ?Sized, type Target = T;impl<T> Deref for Vec<T> type Target = [T];
impl<'a, T> Deref for PeekMut<'a, T> where
T: Ord, type Target = T;impl Deref for String type Target = str;
impl<'a> Deref for CompleteStr<'a> type Target = &'a str;
impl<'a> Deref for CompleteByteSlice<'a> type Target = &'a [u8];