1.0.0[−][src]Trait std::convert::AsRef
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);Run
Required methods
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impl AsRef<[u8]> for str
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impl AsRef<[u8]> for String
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impl AsRef<str> for str
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impl AsRef<str> for String
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impl AsRef<CStr> for CStr
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impl AsRef<CStr> for CString
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impl AsRef<OsStr> for str
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impl AsRef<OsStr> for OsStr
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impl AsRef<OsStr> for OsString
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impl AsRef<OsStr> for Path
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impl AsRef<OsStr> for PathBuf
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impl AsRef<OsStr> for String
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impl AsRef<Path> for str
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impl AsRef<Path> for OsStr
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impl AsRef<Path> for OsString
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impl AsRef<Path> for Path
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impl AsRef<Path> for PathBuf
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impl AsRef<Path> for String
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impl<'_> AsRef<OsStr> for Component<'_>
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impl<'_> AsRef<OsStr> for Components<'_>
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impl<'_> AsRef<OsStr> for std::path::Iter<'_>
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impl<'_> AsRef<Path> for Cow<'_, OsStr>
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impl<'_> AsRef<Path> for Component<'_>
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impl<'_> AsRef<Path> for Components<'_>
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impl<'_> AsRef<Path> for std::path::Iter<'_>
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impl<'_, T> AsRef<[T]> for std::slice::Iter<'_, T>
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impl<'_, T> AsRef<T> for Cow<'_, T> where
T: ToOwned + ?Sized,
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T: ToOwned + ?Sized,
impl<'_, T, U> AsRef<U> for &'_ T where
T: AsRef<U> + ?Sized,
U: ?Sized,
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T: AsRef<U> + ?Sized,
U: ?Sized,
impl<'_, T, U> AsRef<U> for &'_ mut T where
T: AsRef<U> + ?Sized,
U: ?Sized,
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T: AsRef<U> + ?Sized,
U: ?Sized,
impl<T> AsRef<[T]> for [T; 0]
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impl<T> AsRef<[T]> for [T; 1]
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impl<T> AsRef<[T]> for [T; 2]
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impl<T> AsRef<[T]> for [T; 3]
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impl<T> AsRef<[T]> for [T; 4]
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impl<T> AsRef<[T]> for [T; 5]
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impl<T> AsRef<[T]> for [T; 6]
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impl<T> AsRef<[T]> for [T; 7]
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impl<T> AsRef<[T]> for [T; 8]
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impl<T> AsRef<[T]> for [T; 9]
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impl<T> AsRef<[T]> for [T; 10]
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impl<T> AsRef<[T]> for [T; 11]
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impl<T> AsRef<[T]> for [T; 12]
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impl<T> AsRef<[T]> for [T; 13]
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impl<T> AsRef<[T]> for [T; 14]
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impl<T> AsRef<[T]> for [T; 15]
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impl<T> AsRef<[T]> for [T; 16]
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impl<T> AsRef<[T]> for [T; 17]
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impl<T> AsRef<[T]> for [T; 18]
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impl<T> AsRef<[T]> for [T; 19]
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impl<T> AsRef<[T]> for [T; 20]
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impl<T> AsRef<[T]> for [T; 21]
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impl<T> AsRef<[T]> for [T; 22]
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impl<T> AsRef<[T]> for [T; 23]
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impl<T> AsRef<[T]> for [T; 24]
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impl<T> AsRef<[T]> for [T; 25]
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impl<T> AsRef<[T]> for [T; 26]
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impl<T> AsRef<[T]> for [T; 27]
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impl<T> AsRef<[T]> for [T; 28]
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impl<T> AsRef<[T]> for [T; 29]
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impl<T> AsRef<[T]> for [T; 30]
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impl<T> AsRef<[T]> for [T; 31]
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impl<T> AsRef<[T]> for [T; 32]
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impl<T> AsRef<[T]> for [T]
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impl<T> AsRef<[T]> for Vec<T>
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impl<T> AsRef<Vec<T>> for Vec<T>
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impl<T> AsRef<T> for Box<T> where
T: ?Sized,
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T: ?Sized,
impl<T> AsRef<T> for Rc<T> where
T: ?Sized,
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T: ?Sized,
impl<T> AsRef<T> for Arc<T> where
T: ?Sized,
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T: ?Sized,