Expand description
Used to do a cheap reference-to-reference conversion.
This trait is similar to AsMut
which is used for converting between mutable references.
If you need to do a costly conversion it is better to implement From
with type
&T
or write a custom function.
AsRef
has the same signature as Borrow
, but Borrow
is different in few aspects:
- Unlike
AsRef
,Borrow
has a blanket impl for anyT
, and can be used to accept either a reference or a value. Borrow
also requires thatHash
,Eq
andOrd
for borrowed value are equivalent to those of the owned value. For this reason, if you want to borrow only a single field of a struct you can implementAsRef
, but notBorrow
.
Note: This trait must not fail. If the conversion can fail, use a
dedicated method which returns an Option<T>
or a Result<T, E>
.
Generic Implementations
AsRef
auto-dereferences if the inner type is a reference or a mutable reference (e.g.:foo.as_ref()
will work the same iffoo
has type&mut Foo
or&&mut Foo
)
Examples
By using trait bounds we can accept arguments of different types as long as they can be
converted to the specified type T
.
For example: By creating a generic function that takes an AsRef<str>
we express that we
want to accept all references that can be converted to &str
as an argument.
Since both String
and &str
implement AsRef<str>
we can accept both as input argument.
fn is_hello<T: AsRef<str>>(s: T) {
assert_eq!("hello", s.as_ref());
}
let s = "hello";
is_hello(s);
let s = "hello".to_string();
is_hello(s);
Required methods
Implementations on Foreign Types
const: unstable · sourceimpl<'_, T, U> AsRef<U> for &'_ mut T where
T: AsRef<U> + ?Sized,
U: ?Sized,
impl<'_, T, U> AsRef<U> for &'_ mut T where
T: AsRef<U> + ?Sized,
U: ?Sized,
sourceimpl AsRef<SystemTime> for Timestamp
impl AsRef<SystemTime> for Timestamp
fn as_ref(&self) -> &SystemTime
sourceimpl AsRef<OcspResponseRef> for OcspResponse
impl AsRef<OcspResponseRef> for OcspResponse
fn as_ref(&self) -> &OcspResponseRef
sourceimpl AsRef<SrtpProtectionProfileRef> for SrtpProtectionProfile
impl AsRef<SrtpProtectionProfileRef> for SrtpProtectionProfile
fn as_ref(&self) -> &SrtpProtectionProfileRef
sourceimpl AsRef<EcPointRef> for EcPoint
impl AsRef<EcPointRef> for EcPoint
fn as_ref(&self) -> &EcPointRef
sourceimpl AsRef<Asn1TimeRef> for Asn1Time
impl AsRef<Asn1TimeRef> for Asn1Time
fn as_ref(&self) -> &Asn1TimeRef
sourceimpl AsRef<X509NameRef> for X509Name
impl AsRef<X509NameRef> for X509Name
fn as_ref(&self) -> &X509NameRef
sourceimpl AsRef<X509ReqRef> for X509Req
impl AsRef<X509ReqRef> for X509Req
fn as_ref(&self) -> &X509ReqRef
sourceimpl AsRef<X509StoreBuilderRef> for X509StoreBuilder
impl AsRef<X509StoreBuilderRef> for X509StoreBuilder
fn as_ref(&self) -> &X509StoreBuilderRef
sourceimpl AsRef<X509ExtensionRef> for X509Extension
impl AsRef<X509ExtensionRef> for X509Extension
fn as_ref(&self) -> &X509ExtensionRef
sourceimpl AsRef<Asn1GeneralizedTimeRef> for Asn1GeneralizedTime
impl AsRef<Asn1GeneralizedTimeRef> for Asn1GeneralizedTime
fn as_ref(&self) -> &Asn1GeneralizedTimeRef
sourceimpl AsRef<OcspCertIdRef> for OcspCertId
impl AsRef<OcspCertIdRef> for OcspCertId
fn as_ref(&self) -> &OcspCertIdRef
sourceimpl AsRef<OcspBasicResponseRef> for OcspBasicResponse
impl AsRef<OcspBasicResponseRef> for OcspBasicResponse
fn as_ref(&self) -> &OcspBasicResponseRef
sourceimpl AsRef<OcspOneReqRef> for OcspOneReq
impl AsRef<OcspOneReqRef> for OcspOneReq
fn as_ref(&self) -> &OcspOneReqRef
sourceimpl AsRef<OpensslStringRef> for OpensslString
impl AsRef<OpensslStringRef> for OpensslString
fn as_ref(&self) -> &OpensslStringRef
sourceimpl AsRef<EcGroupRef> for EcGroup
impl AsRef<EcGroupRef> for EcGroup
fn as_ref(&self) -> &EcGroupRef
sourceimpl AsRef<X509AlgorithmRef> for X509Algorithm
impl AsRef<X509AlgorithmRef> for X509Algorithm
fn as_ref(&self) -> &X509AlgorithmRef
sourceimpl AsRef<X509NameEntryRef> for X509NameEntry
impl AsRef<X509NameEntryRef> for X509NameEntry
fn as_ref(&self) -> &X509NameEntryRef
sourceimpl AsRef<Asn1ObjectRef> for Asn1Object
impl AsRef<Asn1ObjectRef> for Asn1Object
fn as_ref(&self) -> &Asn1ObjectRef
sourceimpl<T> AsRef<X509LookupMethodRef<T>> for X509LookupMethod<T>
impl<T> AsRef<X509LookupMethodRef<T>> for X509LookupMethod<T>
fn as_ref(&self) -> &X509LookupMethodRef<T>
sourceimpl AsRef<X509VerifyParamRef> for X509VerifyParam
impl AsRef<X509VerifyParamRef> for X509VerifyParam
fn as_ref(&self) -> &X509VerifyParamRef
sourceimpl AsRef<EcdsaSigRef> for EcdsaSig
impl AsRef<EcdsaSigRef> for EcdsaSig
fn as_ref(&self) -> &EcdsaSigRef
sourceimpl AsRef<AccessDescriptionRef> for AccessDescription
impl AsRef<AccessDescriptionRef> for AccessDescription
fn as_ref(&self) -> &AccessDescriptionRef
sourceimpl<T> AsRef<X509LookupRef<T>> for X509Lookup<T>
impl<T> AsRef<X509LookupRef<T>> for X509Lookup<T>
fn as_ref(&self) -> &X509LookupRef<T>
sourceimpl AsRef<BigNumContextRef> for BigNumContext
impl AsRef<BigNumContextRef> for BigNumContext
fn as_ref(&self) -> &BigNumContextRef
sourceimpl AsRef<SslSessionRef> for SslSession
impl AsRef<SslSessionRef> for SslSession
fn as_ref(&self) -> &SslSessionRef
sourceimpl AsRef<GeneralNameRef> for GeneralName
impl AsRef<GeneralNameRef> for GeneralName
fn as_ref(&self) -> &GeneralNameRef
sourceimpl AsRef<CmsContentInfoRef> for CmsContentInfo
impl AsRef<CmsContentInfoRef> for CmsContentInfo
fn as_ref(&self) -> &CmsContentInfoRef
sourceimpl AsRef<X509StoreRef> for X509Store
impl AsRef<X509StoreRef> for X509Store
fn as_ref(&self) -> &X509StoreRef
sourceimpl AsRef<SslContextRef> for SslContext
impl AsRef<SslContextRef> for SslContext
fn as_ref(&self) -> &SslContextRef
sourceimpl AsRef<X509StoreContextRef> for X509StoreContext
impl AsRef<X509StoreContextRef> for X509StoreContext
fn as_ref(&self) -> &X509StoreContextRef
sourceimpl AsRef<Asn1BitStringRef> for Asn1BitString
impl AsRef<Asn1BitStringRef> for Asn1BitString
fn as_ref(&self) -> &Asn1BitStringRef
sourceimpl AsRef<Asn1StringRef> for Asn1String
impl AsRef<Asn1StringRef> for Asn1String
fn as_ref(&self) -> &Asn1StringRef
sourceimpl AsRef<X509ObjectRef> for X509Object
impl AsRef<X509ObjectRef> for X509Object
fn as_ref(&self) -> &X509ObjectRef
sourceimpl AsRef<Asn1IntegerRef> for Asn1Integer
impl AsRef<Asn1IntegerRef> for Asn1Integer
fn as_ref(&self) -> &Asn1IntegerRef
sourceimpl AsRef<OcspRequestRef> for OcspRequest
impl AsRef<OcspRequestRef> for OcspRequest
fn as_ref(&self) -> &OcspRequestRef
Implementors
impl AsRef<str> for Signal
impl AsRef<str> for Url
Return the serialization of this URL.
impl AsRef<OsStr> for OsStr
impl AsRef<OsStr> for PathBuf
impl AsRef<OsStr> for TempPath
impl AsRef<HtmlStr> for Html
impl AsRef<HtmlStr> for HtmlLit
impl AsRef<HtmlStr> for HtmlStr
impl AsRef<Opts> for Opts
impl AsRef<sigset_t> for SigSet
impl AsRef<timespec> for TimeSpec
impl AsRef<timeval> for TimeVal
impl AsRef<Path> for NamedTempFile
impl AsRef<Path> for OsStr
impl AsRef<Path> for PathBuf
impl AsRef<Path> for TempDir
impl AsRef<Path> for TempPath
impl AsRef<dyn Error + 'static> for otter_api_tests::imports::anyhow::Error
impl AsRef<dyn Error + Send + Sync + 'static> for otter_api_tests::imports::anyhow::Error
impl<'_> AsRef<Path> for Cow<'_, OsStr>
impl<'_, T> AsRef<[T]> for otter_api_tests::imports::inventory::core::slice::Iter<'_, T>
impl<'_, T> AsRef<[T]> for IterMut<'_, T>
impl<'_, T> AsRef<T> for Cow<'_, T> where
T: ToOwned + ?Sized,
impl<I, A> AsRef<[A]> for IndexSlice<I, [A]> where
I: Idx,
impl<I, A> AsRef<[A]> for IndexVec<I, A> where
I: Idx,
impl<I, A> AsRef<IndexSlice<I, [A]>> for IndexVec<I, A> where
I: Idx,
impl<L, R> AsRef<str> for Either<L, R> where
L: AsRef<str>,
R: AsRef<str>,
impl<L, R> AsRef<OsStr> for Either<L, R> where
L: AsRef<OsStr>,
R: AsRef<OsStr>,
Requires crate feature use_std
.
impl<L, R> AsRef<CStr> for Either<L, R> where
L: AsRef<CStr>,
R: AsRef<CStr>,
Requires crate feature use_std
.
impl<L, R> AsRef<Path> for Either<L, R> where
L: AsRef<Path>,
R: AsRef<Path>,
Requires crate feature use_std
.