[−][src]Trait into_owned::IntoOwned
A trait for associating a type with its owned variant.
Examples
Implementing the IntoOwned trait for an owned type is straighitforward.
Maybe a derive macro is supplied in future.
use into_owned::{IntoOwned, Is}; #[derive(Clone)] struct A(); impl IntoOwned for A { type Owned = Self; fn is_owned(&self) -> bool { true } fn into_owned(self) -> Self { self } fn try_as_mut(&mut self) -> Option<&mut Self> { Some(self) } fn as_is<'a>(self) -> Is<'a, Self> { Is::Owned(self) } }
Since there are blanket implementations for &T and &mut T where
T: IntoOwned<Owned = T> + Clone,
manually implementing IntoOwned for the owned type is sufficient in most cases.
// this function can be called with an owned value or a borrowed reference fn is_owned<T>(t: T) -> bool where T: IntoOwned { t.is_owned() } assert_eq!(is_owned(A()), true); assert_eq!(is_owned(&A()), false); assert_eq!(is_owned(&mut A()), false);
Associated Types
type Owned
The owned type associated with Self.
Required methods
fn is_owned(&self) -> bool
Returns true if self is an owned value
(e.g. if Self and Self::Owned are the same),
or false otherwise.
This method is used as a hint of whether into_owned method is cheap or not.
fn into_owned(self) -> Self::Owned
Converts self into an owned value.
If Self and Self::Owned are the same, usually it just returns self.
If not, usually it returns an owned value by cloning.
fn try_as_mut(&mut self) -> Option<&mut Self::Owned>
Returns a mutable reference to the owned value of self if possible.
This method should be cheap.
If a mutable reference is required and taking the reference must be cheap,
BorrowMut trait should be used instead.
fn as_is<'a>(self) -> Is<'a, Self>
Returns self as Is<'a, Self>.
This method is useful when self is used differently depending on
its state: owned, (immutably) borrowed, or mutably borrowed.
Examples
use into_owned::{IntoOwned, Is}; // returns: // * `0` if `t` is an owned value // * `1` if `t` is an immutably borrowed reference // * `2` if `t` is a mutably borrowed reference fn a<T>(t: T) -> i8 where T: IntoOwned { match t.as_is() { Is::Owned(x) => { // here `x: T::Owned` 0 } Is::Borrowed(x) => { // here `x: &T::Owned` 1 } Is::MutBorrowed(x) => { // here `x: &mut T::Owned` 2 } } } assert_eq!(a(1.0), 0); assert_eq!(a(&1.0), 1); assert_eq!(a(&mut 1.0), 2);
Implementations on Foreign Types
impl<'_, T> IntoOwned for &'_ T where
T: IntoOwned<Owned = T> + Clone, [src]
T: IntoOwned<Owned = T> + Clone,
type Owned = T
fn is_owned(&self) -> bool[src]
fn into_owned(self) -> T[src]
fn try_as_mut(&mut self) -> Option<&mut Self::Owned>[src]
fn as_is<'a>(self) -> Is<'a, Self>[src]
impl<'_, T> IntoOwned for &'_ mut T where
T: IntoOwned<Owned = T> + Clone, [src]
T: IntoOwned<Owned = T> + Clone,