Struct owning_ref::OwningRef[−][src]

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

Expand description

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

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

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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.

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

Like new, but dosen’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 to use when coherence rules prevent implememnting the trait without adding a dependency to this crate in a third-party library.

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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.

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>,

Variant of map() that may fail.

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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.

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

Converts self into a new owning reference where the onwer 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<Erased>, T>.

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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<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);
}