pub struct VacantEntry<'a, K, V> where
K: Key, { /* private fields */ }
Expand description
A view into a vacant entry in a SecondaryMap
. It is part of the
Entry
enum.
Implementations
sourceimpl<'a, K, V> VacantEntry<'a, K, V> where
K: Key,
impl<'a, K, V> VacantEntry<'a, K, V> where
K: Key,
sourcepub fn key(&self) -> K
pub fn key(&self) -> K
Gets the key that would be used when inserting a value through the
VacantEntry
.
Examples
let mut sm = SlotMap::new();
let mut sec: SecondaryMap<_, ()> = SecondaryMap::new();
let k = sm.insert(1);
if let Entry::Vacant(v) = sec.entry(k).unwrap() {
assert_eq!(v.key(), k);
}
sourcepub fn insert(self, value: V) -> &'a mut V
pub fn insert(self, value: V) -> &'a mut V
Sets the value of the entry with the VacantEntry
’s key, and returns
a mutable reference to it.
Examples
let mut sm = SlotMap::new();
let mut sec = SecondaryMap::new();
let k = sm.insert(1);
if let Entry::Vacant(v) = sec.entry(k).unwrap() {
let new_val = v.insert(3);
assert_eq!(new_val, &mut 3);
}
sourcepub fn remove_stale_entry(&mut self) -> Option<(K, V)>
pub fn remove_stale_entry(&mut self) -> Option<(K, V)>
Returns the stale key and data, if any, which would be overwritten by
inserting using this VacantEntry
.
This situation arises if the stale key was removed from the primary map, and a subsequent insert into the primary map reused the slot.
remove_stale_entry
can be used to handle this situation specially —
for example, if the application wants to lazily clean up tertiary data
in another data structure indexed by the now-stale key, or by the value
stored in the SecondaryMap
.
Most applications will not need this.
Examples
let mut pri = SlotMap::new();
let mut sec = SecondaryMap::new();
let k1 = pri.insert(1);
let ent = sec.entry(k1);
let mut vacant = match ent { Some(Entry::Vacant(vac)) => vac, _ => panic!("1. {:?}", &ent) };
assert_eq!(vacant.remove_stale_entry(), None);
sec.insert(k1, 'a');
pri.remove(k1);
// Imagine we don't keep a note of k1, after this.
let k2 = pri.insert(2);
let ent = sec.entry(k2);
let mut vacant = match ent { Some(Entry::Vacant(vac)) => vac, _ => panic!("2. {:?}", &ent) };
// Now we have recovered k1 and the associated data:
assert_eq!(vacant.remove_stale_entry(), Some((k1, 'a')));
assert_eq!(vacant.remove_stale_entry(), None);
vacant.insert('b');
assert!(sec.entry(k1).is_none());
Trait Implementations
Auto Trait Implementations
impl<'a, K, V> RefUnwindSafe for VacantEntry<'a, K, V> where
V: RefUnwindSafe,
impl<'a, K, V> Send for VacantEntry<'a, K, V> where
V: Send,
impl<'a, K, V> Sync for VacantEntry<'a, K, V> where
V: Sync,
impl<'a, K, V> Unpin for VacantEntry<'a, K, V>
impl<'a, K, V> !UnwindSafe for VacantEntry<'a, K, V>
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<T> Downcast for T where
T: Any,
impl<T> Downcast for T where
T: Any,
sourcefn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<W, Global>impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<W, Global>impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
Convert Box<dyn Trait>
(where Trait: Downcast
) to Box<dyn Any>
. Box<dyn Any>
can
then be further downcast
into Box<ConcreteType>
where ConcreteType
implements Trait
. Read more
sourcefn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
Convert Rc<Trait>
(where Trait: Downcast
) to Rc<Any>
. Rc<Any>
can then be
further downcast
into Rc<ConcreteType>
where ConcreteType
implements Trait
. Read more
sourcefn as_any(&self) -> &(dyn Any + 'static)
fn as_any(&self) -> &(dyn Any + 'static)
Convert &Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &Any
’s vtable from &Trait
’s. Read more
sourcefn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
Convert &mut Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &mut Any
’s vtable from &mut Trait
’s. Read more
sourceimpl<T> DowncastSync for T where
T: Any + Send + Sync,
impl<T> DowncastSync for T where
T: Any + Send + Sync,
sourceimpl<A> DynCastExt for A
impl<A> DynCastExt for A
sourcefn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
A: DynCastExtHelper<T>,
T: ?Sized,
fn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
A: DynCastExtHelper<T>,
T: ?Sized,
Use this to cast from one trait object type to another. Read more
sourcefn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
T: ?Sized,
fn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
T: ?Sized,
Use this to upcast a trait to one of its supertraits. Read more
sourcefn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
T: ?Sized,
fn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
T: ?Sized,
sourcefn dyn_cast_with_config<C>(
self
) -> Result<<A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Target, <A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Source> where
C: DynCastConfig,
A: DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>,
fn dyn_cast_with_config<C>(
self
) -> Result<<A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Target, <A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Source> where
C: DynCastConfig,
A: DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>,
Use this to cast from one trait object type to another. With this method the type parameter is a config type that uniquely specifies which cast should be preformed. Read more