Trait artifact_app::dev_prefix::DerefMut

#[lang = "deref_mut"]
pub trait DerefMut: Deref {
    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 accomodate 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:

• In mutable contexts, *x on non-pointer types is equivalent to *Deref::deref(&x).
• Values of type &mut T are coerced to values of type &mut U
• T implicitly implements all the (mutable) 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, the Deref trait, 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) -> &T {
        &self.value
    }
}

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

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

Required Methods

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

Implementations on Foreign Types

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

fn deref_mut(&mut self) -> &mut [<A as Array>::Item]

impl<T> DerefMut for ManuallyDrop<T>

fn deref_mut(&mut self) -> &mut <ManuallyDrop<T> as Deref>::Target

impl<'b, T> DerefMut for RefMut<'b, T> where
    T: ?Sized, 

fn deref_mut(&mut self) -> &mut T

impl<'a, T> DerefMut for &'a mut T where
    T: ?Sized, 

fn deref_mut(&mut self) -> &mut T

impl<S> DerefMut for UniCase<S>

fn deref_mut(&'a mut self) -> &'a mut S

impl<T> DerefMut for BiLockAcquired<T>

fn deref_mut(&mut self) -> &mut T

impl<'a, T> DerefMut for BiLockGuard<'a, T>

fn deref_mut(&mut self) -> &mut T

impl<'a, T> DerefMut for PeekMut<'a, T> where
    T: Ord, 

fn deref_mut(&mut self) -> &mut T

impl<T> DerefMut for Vec<T>

fn deref_mut(&mut self) -> &mut [T]

impl DerefMut for String

fn deref_mut(&mut self) -> &mut str

impl<T> DerefMut for Box<T> where
    T: ?Sized, 

fn deref_mut(&mut self) -> &mut T

impl<S> DerefMut for Ascii<S>

fn deref_mut(&'a mut self) -> &'a mut S

impl<S> DerefMut for UniCase<S>

fn deref_mut(&'a mut self) -> &'a mut S

impl DerefMut for BytesMut

fn deref_mut(&mut self) -> &mut [u8]

impl<'rwlock, T> DerefMut for RwLockWriteGuard<'rwlock, T> where
    T: ?Sized, 

fn deref_mut(&mut self) -> &mut T

impl<'mutex, T> DerefMut for MutexGuard<'mutex, T> where
    T: ?Sized, 

fn deref_mut(&mut self) -> &mut T

impl<T> DerefMut for AssertUnwindSafe<T>

fn deref_mut(&mut self) -> &mut T

impl DerefMut for AccessControlAllowHeaders

fn deref_mut(&mut self) -> &mut Vec<UniCase<String>>

impl DerefMut for ETag

fn deref_mut(&mut self) -> &mut EntityTag

impl DerefMut for PreferenceApplied

fn deref_mut(&mut self) -> &mut Vec<Preference>

impl DerefMut for TransferEncoding

fn deref_mut(&mut self) -> &mut Vec<Encoding>

impl DerefMut for AccessControlMaxAge

fn deref_mut(&mut self) -> &mut u32

impl DerefMut for Allow

fn deref_mut(&mut self) -> &mut Vec<Method>

impl DerefMut for IfUnmodifiedSince

fn deref_mut(&mut self) -> &mut HttpDate

impl DerefMut for From

fn deref_mut(&mut self) -> &mut String

impl DerefMut for Cookie

fn deref_mut(&mut self) -> &mut Vec<String>

impl DerefMut for Location

fn deref_mut(&mut self) -> &mut String

impl DerefMut for AccessControlExposeHeaders

fn deref_mut(&mut self) -> &mut Vec<UniCase<String>>

impl DerefMut for IfModifiedSince

fn deref_mut(&mut self) -> &mut HttpDate

impl<S> DerefMut for Authorization<S> where
    S: Scheme, 

fn deref_mut(&mut self) -> &mut S

impl DerefMut for AcceptCharset

fn deref_mut(&mut self) -> &mut Vec<QualityItem<Charset>>

impl DerefMut for Upgrade

fn deref_mut(&mut self) -> &mut Vec<Protocol>

impl DerefMut for Date

fn deref_mut(&mut self) -> &mut HttpDate

impl DerefMut for CacheControl

fn deref_mut(&mut self) -> &mut Vec<CacheDirective>

impl DerefMut for LastModified

fn deref_mut(&mut self) -> &mut HttpDate

impl DerefMut for AcceptRanges

fn deref_mut(&mut self) -> &mut Vec<RangeUnit>

impl DerefMut for ContentType

fn deref_mut(&mut self) -> &mut Mime<Vec<(Attr, Value)>>

impl DerefMut for Referer

fn deref_mut(&mut self) -> &mut String

impl DerefMut for Expires

fn deref_mut(&mut self) -> &mut HttpDate

impl DerefMut for ContentLanguage

fn deref_mut(&mut self) -> &mut Vec<QualityItem<LanguageTag>>

impl DerefMut for AcceptEncoding

fn deref_mut(&mut self) -> &mut Vec<QualityItem<Encoding>>

impl DerefMut for AccessControlRequestHeaders

fn deref_mut(&mut self) -> &mut Vec<UniCase<String>>

impl DerefMut for ContentRange

fn deref_mut(&mut self) -> &mut ContentRangeSpec

impl DerefMut for AccessControlRequestMethod

fn deref_mut(&mut self) -> &mut Method

impl DerefMut for Prefer

fn deref_mut(&mut self) -> &mut Vec<Preference>

impl DerefMut for UserAgent

fn deref_mut(&mut self) -> &mut String

impl DerefMut for AcceptLanguage

fn deref_mut(&mut self) -> &mut Vec<QualityItem<LanguageTag>>

impl DerefMut for Connection

fn deref_mut(&mut self) -> &mut Vec<ConnectionOption>

impl DerefMut for ContentEncoding

fn deref_mut(&mut self) -> &mut Vec<Encoding>

impl DerefMut for Accept

fn deref_mut(&mut self) -> &mut Vec<QualityItem<Mime<Vec<(Attr, Value)>>>>

impl DerefMut for Server

fn deref_mut(&mut self) -> &mut String

impl DerefMut for SetCookie

fn deref_mut(&mut self) -> &mut Vec<String>

impl DerefMut for AccessControlAllowMethods

fn deref_mut(&mut self) -> &mut Vec<Method>

impl DerefMut for ContentLength

fn deref_mut(&mut self) -> &mut u64

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

fn deref_mut(&mut self) -> &mut <Either<L, R> as Deref>::Target

impl DerefMut for IoVec

fn deref_mut(&mut self) -> &mut [u8]

impl DerefMut for UnixReady

fn deref_mut(&mut self) -> &mut Ready

impl DerefMut for AcceptLanguage

fn deref_mut(&mut self) -> &mut Vec<QualityItem<LanguageTag>>

impl DerefMut for Expires

fn deref_mut(&mut self) -> &mut HttpDate

impl DerefMut for AccessControlMaxAge

fn deref_mut(&mut self) -> &mut u32

impl DerefMut for ContentLocation

fn deref_mut(&mut self) -> &mut String

impl DerefMut for AccessControlAllowHeaders

fn deref_mut(&mut self) -> &mut Vec<Ascii<String>>

impl DerefMut for TransferEncoding

fn deref_mut(&mut self) -> &mut Vec<Encoding>

impl DerefMut for Allow

fn deref_mut(&mut self) -> &mut Vec<Method>

impl DerefMut for ContentLanguage

fn deref_mut(&mut self) -> &mut Vec<QualityItem<LanguageTag>>

impl DerefMut for ContentRange

fn deref_mut(&mut self) -> &mut ContentRangeSpec

impl DerefMut for PreferenceApplied

fn deref_mut(&mut self) -> &mut Vec<Preference>

impl DerefMut for ETag

fn deref_mut(&mut self) -> &mut EntityTag

impl DerefMut for AccessControlAllowMethods

fn deref_mut(&mut self) -> &mut Vec<Method>

impl DerefMut for LastModified

fn deref_mut(&mut self) -> &mut HttpDate

impl DerefMut for AccessControlRequestMethod

fn deref_mut(&mut self) -> &mut Method

impl DerefMut for SetCookie

fn deref_mut(&mut self) -> &mut Vec<String>

impl DerefMut for Connection

fn deref_mut(&mut self) -> &mut Vec<ConnectionOption>

impl<S> DerefMut for Authorization<S> where
    S: Scheme, 

fn deref_mut(&mut self) -> &mut S

impl DerefMut for Date

fn deref_mut(&mut self) -> &mut HttpDate

impl DerefMut for ContentEncoding

fn deref_mut(&mut self) -> &mut Vec<Encoding>

impl DerefMut for ContentLength

fn deref_mut(&mut self) -> &mut u64

impl DerefMut for AcceptEncoding

fn deref_mut(&mut self) -> &mut Vec<QualityItem<Encoding>>

impl DerefMut for From

fn deref_mut(&mut self) -> &mut String

impl DerefMut for LastEventId

fn deref_mut(&mut self) -> &mut String

impl DerefMut for Upgrade

fn deref_mut(&mut self) -> &mut Vec<Protocol>

impl DerefMut for CacheControl

fn deref_mut(&mut self) -> &mut Vec<CacheDirective>

impl DerefMut for IfModifiedSince

fn deref_mut(&mut self) -> &mut HttpDate

impl DerefMut for AccessControlRequestHeaders

fn deref_mut(&mut self) -> &mut Vec<Ascii<String>>

impl DerefMut for AccessControlExposeHeaders

fn deref_mut(&mut self) -> &mut Vec<Ascii<String>>

impl DerefMut for Accept

fn deref_mut(&mut self) -> &mut Vec<QualityItem<Mime>>

impl DerefMut for IfUnmodifiedSince

fn deref_mut(&mut self) -> &mut HttpDate

impl DerefMut for Prefer

fn deref_mut(&mut self) -> &mut Vec<Preference>

impl DerefMut for AcceptRanges

fn deref_mut(&mut self) -> &mut Vec<RangeUnit>

impl DerefMut for AcceptCharset

fn deref_mut(&mut self) -> &mut Vec<QualityItem<Charset>>

impl DerefMut for Te

fn deref_mut(&mut self) -> &mut Vec<QualityItem<Encoding>>

impl DerefMut for ContentType

fn deref_mut(&mut self) -> &mut Mime

impl<M> DerefMut for IoHandler<M> where
    M: Metadata, 

fn deref_mut(&mut self) -> &mut <IoHandler<M> as Deref>::Target

impl DerefMut for Lit

fn deref_mut(&mut self) -> &mut Vec<u8>

impl<T, B> DerefMut for Message<T, B>

fn deref_mut(&mut self) -> &mut T

Implementors