Struct holochain::prelude::kitsune_p2p::dependencies::kitsune_p2p_types::dependencies::lair_keystore_api::dependencies::once_cell::sync::Lazy
source · pub struct Lazy<T, F = fn() -> T> { /* private fields */ }
Expand description
A value which is initialized on the first access.
This type is thread-safe and can be used in statics.
Example
use std::collections::HashMap;
use once_cell::sync::Lazy;
static HASHMAP: Lazy<HashMap<i32, String>> = Lazy::new(|| {
println!("initializing");
let mut m = HashMap::new();
m.insert(13, "Spica".to_string());
m.insert(74, "Hoyten".to_string());
m
});
fn main() {
println!("ready");
std::thread::spawn(|| {
println!("{:?}", HASHMAP.get(&13));
}).join().unwrap();
println!("{:?}", HASHMAP.get(&74));
// Prints:
// ready
// initializing
// Some("Spica")
// Some("Hoyten")
}
Implementations§
source§impl<T, F> Lazy<T, F>where
F: FnOnce() -> T,
impl<T, F> Lazy<T, F>where F: FnOnce() -> T,
sourcepub fn force(this: &Lazy<T, F>) -> &T
pub fn force(this: &Lazy<T, F>) -> &T
Forces the evaluation of this lazy value and
returns a reference to the result. This is equivalent
to the Deref
impl, but is explicit.
Example
use once_cell::sync::Lazy;
let lazy = Lazy::new(|| 92);
assert_eq!(Lazy::force(&lazy), &92);
assert_eq!(&*lazy, &92);
sourcepub fn force_mut(this: &mut Lazy<T, F>) -> &mut T
pub fn force_mut(this: &mut Lazy<T, F>) -> &mut T
Forces the evaluation of this lazy value and
returns a mutable reference to the result. This is equivalent
to the Deref
impl, but is explicit.
Example
use once_cell::sync::Lazy;
let mut lazy = Lazy::new(|| 92);
assert_eq!(Lazy::force_mut(&mut lazy), &mut 92);
sourcepub fn get(this: &Lazy<T, F>) -> Option<&T>
pub fn get(this: &Lazy<T, F>) -> Option<&T>
Gets the reference to the result of this lazy value if
it was initialized, otherwise returns None
.
Example
use once_cell::sync::Lazy;
let lazy = Lazy::new(|| 92);
assert_eq!(Lazy::get(&lazy), None);
assert_eq!(&*lazy, &92);
assert_eq!(Lazy::get(&lazy), Some(&92));
sourcepub fn get_mut(this: &mut Lazy<T, F>) -> Option<&mut T>
pub fn get_mut(this: &mut Lazy<T, F>) -> Option<&mut T>
Gets the reference to the result of this lazy value if
it was initialized, otherwise returns None
.
Example
use once_cell::sync::Lazy;
let mut lazy = Lazy::new(|| 92);
assert_eq!(Lazy::get_mut(&mut lazy), None);
assert_eq!(&*lazy, &92);
assert_eq!(Lazy::get_mut(&mut lazy), Some(&mut 92));
Trait Implementations§
impl<T, F> RefUnwindSafe for Lazy<T, F>where F: RefUnwindSafe, OnceCell<T>: RefUnwindSafe,
impl<T, F> Sync for Lazy<T, F>where F: Send, OnceCell<T>: Sync,
Auto Trait Implementations§
impl<T, F> Send for Lazy<T, F>where F: Send, T: Send,
impl<T, F> Unpin for Lazy<T, F>where F: Unpin, T: Unpin,
impl<T, F> UnwindSafe for Lazy<T, F>where F: UnwindSafe, T: UnwindSafe,
Blanket Implementations§
§impl<T> ArchivePointee for T
impl<T> ArchivePointee for T
§type ArchivedMetadata = ()
type ArchivedMetadata = ()
The archived version of the pointer metadata for this type.
§fn pointer_metadata(
_: &<T as ArchivePointee>::ArchivedMetadata
) -> <T as Pointee>::Metadata
fn pointer_metadata( _: &<T as ArchivePointee>::ArchivedMetadata ) -> <T as Pointee>::Metadata
Converts some archived metadata to the pointer metadata for itself.
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
§impl<F, W, T, D> Deserialize<With<T, W>, D> for Fwhere
W: DeserializeWith<F, T, D>,
D: Fallible + ?Sized,
F: ?Sized,
impl<F, W, T, D> Deserialize<With<T, W>, D> for Fwhere W: DeserializeWith<F, T, D>, D: Fallible + ?Sized, F: ?Sized,
§fn deserialize(
&self,
deserializer: &mut D
) -> Result<With<T, W>, <D as Fallible>::Error>
fn deserialize( &self, deserializer: &mut D ) -> Result<With<T, W>, <D as Fallible>::Error>
Deserializes using the given deserializer
source§impl<T> Instrument for T
impl<T> Instrument for T
source§fn instrument(self, span: Span) -> Instrumented<Self> ⓘ
fn instrument(self, span: Span) -> Instrumented<Self> ⓘ
source§fn in_current_span(self) -> Instrumented<Self> ⓘ
fn in_current_span(self) -> Instrumented<Self> ⓘ
source§impl<T> Instrument for T
impl<T> Instrument for T
source§fn instrument(self, span: Span) -> Instrumented<Self> ⓘ
fn instrument(self, span: Span) -> Instrumented<Self> ⓘ
source§fn in_current_span(self) -> Instrumented<Self> ⓘ
fn in_current_span(self) -> Instrumented<Self> ⓘ
§impl<T> Pointable for T
impl<T> Pointable for T
§impl<SS, SP> SupersetOf<SS> for SPwhere
SS: SubsetOf<SP>,
impl<SS, SP> SupersetOf<SS> for SPwhere SS: SubsetOf<SP>,
§fn to_subset(&self) -> Option<SS>
fn to_subset(&self) -> Option<SS>
The inverse inclusion map: attempts to construct
self
from the equivalent element of its
superset. Read more§fn is_in_subset(&self) -> bool
fn is_in_subset(&self) -> bool
Checks if
self
is actually part of its subset T
(and can be converted to it).§fn to_subset_unchecked(&self) -> SS
fn to_subset_unchecked(&self) -> SS
Use with care! Same as
self.to_subset
but without any property checks. Always succeeds.§fn from_subset(element: &SS) -> SP
fn from_subset(element: &SS) -> SP
The inclusion map: converts
self
to the equivalent element of its superset.§impl<T> Upcastable for Twhere
T: Any + Send + Sync + 'static,
impl<T> Upcastable for Twhere T: Any + Send + Sync + 'static,
§fn upcast_any_ref(&self) -> &(dyn Any + 'static)
fn upcast_any_ref(&self) -> &(dyn Any + 'static)
upcast ref
§fn upcast_any_mut(&mut self) -> &mut (dyn Any + 'static)
fn upcast_any_mut(&mut self) -> &mut (dyn Any + 'static)
upcast mut ref