pub struct Lazy<T, F = fn() -> T> { /* private fields */ }
Expand description
A value which is initialized on the first access.
Example
use once_cell::unsync::Lazy;
let lazy: Lazy<i32> = Lazy::new(|| {
println!("initializing");
92
});
println!("ready");
println!("{}", *lazy);
println!("{}", *lazy);
// Prints:
// ready
// initializing
// 92
// 92
Implementations§
§impl<T, F> Lazy<T, F>
impl<T, F> Lazy<T, F>
pub const fn new(init: F) -> Lazy<T, F>
pub const fn new(init: F) -> Lazy<T, F>
Creates a new lazy value with the given initializing function.
Example
use once_cell::unsync::Lazy;
let hello = "Hello, World!".to_string();
let lazy = Lazy::new(|| hello.to_uppercase());
assert_eq!(&*lazy, "HELLO, WORLD!");
pub fn into_value(this: Lazy<T, F>) -> Result<T, F>
pub fn into_value(this: Lazy<T, F>) -> Result<T, F>
Consumes this Lazy
returning the stored value.
Returns Ok(value)
if Lazy
is initialized and Err(f)
otherwise.
§impl<T, F> Lazy<T, F>where
F: FnOnce() -> T,
impl<T, F> Lazy<T, F>where
F: FnOnce() -> T,
pub 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::unsync::Lazy;
let lazy = Lazy::new(|| 92);
assert_eq!(Lazy::force(&lazy), &92);
assert_eq!(&*lazy, &92);
pub 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 DerefMut
impl, but is explicit.
Example
use once_cell::unsync::Lazy;
let mut lazy = Lazy::new(|| 92);
assert_eq!(Lazy::force_mut(&mut lazy), &92);
assert_eq!(*lazy, 92);
pub 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::unsync::Lazy;
let lazy = Lazy::new(|| 92);
assert_eq!(Lazy::get(&lazy), None);
assert_eq!(&*lazy, &92);
assert_eq!(Lazy::get(&lazy), Some(&92));
pub 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 mutable reference to the result of this lazy value if
it was initialized, otherwise returns None
.
Example
use once_cell::unsync::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,
Auto Trait Implementations§
impl<T, F> Send for Lazy<T, F>where
F: Send,
T: Send,
impl<T, F = fn() -> T> !Sync for Lazy<T, F>
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, U> AsBindGroupShaderType<U> for Twhere
U: ShaderType,
&'a T: for<'a> Into<U>,
impl<T, U> AsBindGroupShaderType<U> for Twhere
U: ShaderType,
&'a T: for<'a> Into<U>,
§fn as_bind_group_shader_type(&self, _images: &RenderAssets<Image>) -> U
fn as_bind_group_shader_type(&self, _images: &RenderAssets<Image>) -> U
Return the
T
ShaderType
for self
. When used in AsBindGroup
derives, it is safe to assume that all images in self
exist. Read more§impl<T> Downcast for Twhere
T: Any,
impl<T> Downcast for Twhere
T: Any,
§fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>
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§fn 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§fn 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§fn 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§impl<T> FromWorld for Twhere
T: Default,
impl<T> FromWorld for Twhere
T: Default,
§fn from_world(_world: &mut World) -> T
fn from_world(_world: &mut World) -> T
Creates
Self
using data from the given World