Struct owning_ref::OwningRef

pub struct OwningRef<O, T: ?Sized> { /* fields omitted */ }

An owning reference.

This wraps an owner O and a reference &T pointing at something reachable from O::Target while keeping the ability to move self around.

The owner is usually a pointer that points at some base type.

For more details and examples, see the module and method docs.

Implementations

impl<O, T: ?Sized> OwningRef<O, T>

pub fn new(o: O) -> Self where
    O: StableAddress,
    O: Deref<Target = T>, 

Creates a new owning reference from a owner initialized to the direct dereference of it.

Example

extern crate owning_ref;
use owning_ref::OwningRef;

fn main() {
    let owning_ref = OwningRef::new(Box::new(42));
    assert_eq!(*owning_ref, 42);
}

pub unsafe fn new_assert_stable_address(o: O) -> Self where
    O: Deref<Target = T>, 

Like new, but doesn’t require O to implement the StableAddress trait. Instead, the caller is responsible to make the same promises as implementing the trait.

This is useful for cases where coherence rules prevents implementing the trait without adding a dependency to this crate in a third-party library.

pub fn map<F, U: ?Sized>(self, f: F) -> OwningRef<O, U> where
    O: StableAddress,
    F: FnOnce(&T) -> &U, 

Converts self into a new owning reference that points at something reachable from the previous one.

This can be a reference to a field of U, something reachable from a field of U, or even something unrelated with a 'static lifetime.

Example

extern crate owning_ref;
use owning_ref::OwningRef;

fn main() {
    let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4]));

    // create a owning reference that points at the
    // third element of the array.
    let owning_ref = owning_ref.map(|array| &array[2]);
    assert_eq!(*owning_ref, 3);
}

pub fn map_with_owner<F, U: ?Sized>(self, f: F) -> OwningRef<O, U> where
    O: StableAddress,
    F: for<'a> FnOnce(&'a O, &'a T) -> &'a U, 

Converts self into a new owning reference that points at something reachable from the previous one or from the owner itself.

This can be a reference to a field of U, something reachable from a field of U or from the owner O, or even something unrelated with a 'static lifetime.

Example

extern crate owning_ref;
use owning_ref::OwningRef;

fn main() {
    let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4]));
    let owning_ref = owning_ref.map(|array| &array[2]);
    assert_eq!(*owning_ref, 3);

    // create a owning reference that points at the
    // second element of the array from the owning ref that was pointing to the third
    let owning_ref = owning_ref.map_with_owner(|array, _prev| &array[1]);
    assert_eq!(*owning_ref, 2);
}

pub fn try_map<F, U: ?Sized, E>(self, f: F) -> Result<OwningRef<O, U>, E> where
    O: StableAddress,
    F: FnOnce(&T) -> Result<&U, E>, 

Tries to convert self into a new owning reference that points at something reachable from the previous one.

This can be a reference to a field of U, something reachable from a field of U, or even something unrelated with a 'static lifetime.

Example

extern crate owning_ref;
use owning_ref::OwningRef;

fn main() {
    let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4]));

    // create a owning reference that points at the
    // third element of the array.
    let owning_ref = owning_ref.try_map(|array| {
        if array[2] == 3 { Ok(&array[2]) } else { Err(()) }
    });
    assert_eq!(*owning_ref.unwrap(), 3);
}

pub fn try_map_with_owner<F, U: ?Sized, E>(
    self,
    f: F
) -> Result<OwningRef<O, U>, E> where
    O: StableAddress,
    F: for<'a> FnOnce(&'a O, &'a T) -> Result<&'a U, E>, 

Tries to convert self into a new owning reference that points at something reachable from the previous one.

This can be a reference to a field of U, something reachable from a field of U, or even something unrelated with a 'static lifetime.

Example

extern crate owning_ref;
use owning_ref::OwningRef;

fn main() {
    let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4]));
    let owning_ref = owning_ref.map(|array| &array[2]);

    // create a owning reference that points at the
    // second element of the array from the owning ref that was pointing to the third
    let owning_ref = owning_ref.try_map_with_owner(|array, _prev| {
        if array[1] == 2 { Ok(&array[1]) } else { Err(()) }
    });
    assert_eq!(*owning_ref.unwrap(), 2);
}

pub unsafe fn map_owner<F, P>(self, f: F) -> OwningRef<P, T> where
    O: StableAddress,
    P: StableAddress,
    F: FnOnce(O) -> P, 

Converts self into a new owning reference with a different owner type.

The new owner type needs to still contain the original owner in some way so that the reference into it remains valid. This function is marked unsafe because the user needs to manually uphold this guarantee.

pub fn map_owner_box(self) -> OwningRef<Box<O>, T>

Converts self into a new owning reference where the owner is wrapped in an additional Box<O>.

This can be used to safely erase the owner of any OwningRef<O, T> to a OwningRef<Box<dyn Erased>, T>.

pub fn erase_owner<'a>(self) -> OwningRef<O::Erased, T> where
    O: IntoErased<'a>, 

Erases the concrete base type of the owner with a trait object.

This allows mixing of owned references with different owner base types.

Example

extern crate owning_ref;
use owning_ref::{OwningRef, Erased};

fn main() {
    // NB: Using the concrete types here for explicitnes.
    // For less verbose code type aliases like `BoxRef` are provided.

    let owning_ref_a: OwningRef<Box<[i32; 4]>, [i32; 4]>
        = OwningRef::new(Box::new([1, 2, 3, 4]));

    let owning_ref_b: OwningRef<Box<Vec<(i32, bool)>>, Vec<(i32, bool)>>
        = OwningRef::new(Box::new(vec![(0, false), (1, true)]));

    let owning_ref_a: OwningRef<Box<[i32; 4]>, i32>
        = owning_ref_a.map(|a| &a[0]);

    let owning_ref_b: OwningRef<Box<Vec<(i32, bool)>>, i32>
        = owning_ref_b.map(|a| &a[1].0);

    let owning_refs: [OwningRef<Box<dyn Erased>, i32>; 2]
        = [owning_ref_a.erase_owner(), owning_ref_b.erase_owner()];

    assert_eq!(*owning_refs[0], 1);
    assert_eq!(*owning_refs[1], 1);
}

pub fn as_owner(&self) -> &O

A reference to the underlying owner.

pub fn into_owner(self) -> O

Discards the reference and retrieves the owner.

Trait Implementations

impl<O, T: ?Sized> AsRef<T> for OwningRef<O, T>

fn as_ref(&self) -> &T

Performs the conversion.

impl<O, T: ?Sized> Borrow<T> for OwningRef<O, T>

fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<O, T: ?Sized> Clone for OwningRef<O, T> where
    O: CloneStableAddress, 

fn clone(&self) -> Self

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<O, T: ?Sized> CloneStableDeref for OwningRef<O, T> where
    O: CloneStableAddress, 

impl<O, T: ?Sized> Debug for OwningRef<O, T> where
    O: Debug,
    T: Debug, 

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<O, T: ?Sized> Deref for OwningRef<O, T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<O, T: ?Sized> Eq for OwningRef<O, T> where
    T: Eq, 

impl<O, T: ?Sized> From<O> for OwningRef<O, T> where
    O: StableAddress,
    O: Deref<Target = T>, 

fn from(owner: O) -> Self

Performs the conversion.

impl<O, T: ?Sized> From<OwningRefMut<O, T>> for OwningRef<O, T> where
    O: StableAddress,
    O: DerefMut<Target = T>, 

fn from(other: OwningRefMut<O, T>) -> Self

Performs the conversion.

impl<O, T: ?Sized> Hash for OwningRef<O, T> where
    T: Hash, 

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

pub fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl<O, T: ?Sized> Ord for OwningRef<O, T> where
    T: Ord, 

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

#[must_use]pub fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]pub fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]pub fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl<O, T: ?Sized> PartialEq<OwningRef<O, T>> for OwningRef<O, T> where
    T: PartialEq, 

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use]pub fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<O, T: ?Sized> PartialOrd<OwningRef<O, T>> for OwningRef<O, T> where
    T: PartialOrd, 

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use]pub fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use]pub fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use]pub fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use]pub fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<O, T: ?Sized> Send for OwningRef<O, T> where
    O: Send,
    &'a T: Send, 

impl<O, T: ?Sized> StableDeref for OwningRef<O, T>

impl<O, T: ?Sized> Sync for OwningRef<O, T> where
    O: Sync,
    &'a T: Sync,