Struct LazyTransform

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pub struct LazyTransform<T, U> { /* private fields */ }

Expand description

LazyTransform<T, U> is a synchronized holder type, that holds a value of type T until it is lazily converted into a value of type U.

Implementations§

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impl<T, U> LazyTransform<T, U>

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pub fn new(t: T) -> LazyTransform<T, U>

Construct a new, untransformed LazyTransform<T, U> with an argument of type T.

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pub fn into_inner(self) -> Result<U, T>

Unwrap the contained value, returning Ok(U) if the LazyTransform<T, U> has been transformed.

§Errors

Iff this instance has not been transformed yet.

§Panics

Iff this instance has been poisoned during transformation.

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pub fn try_into_inner(self) -> Result<U, Option<T>>

Unwrap the contained value, returning Ok(Ok(U)) iff the LazyTransform<T, U> has been transformed.

§Errors

Iff this instance has neither been transformed yet nor poisoned, Err(Some(T)) is returned.

Iff this instance has been poisoned by error during a call to .get_or_create_or_poison, Err(None) is returned.

§Panics

Iff this instance has been poisoned by a panic during transformation.

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impl<T, U> LazyTransform<T, U>

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pub fn get_or_create<F>(&self, f: F) -> &U
where F: FnOnce(T) -> U,

Get a reference to the transformed value, invoking f to transform it if the LazyTransform<T, U> has yet to be transformed. It is guaranteed that if multiple calls to get_or_create race, only one will invoke its closure, and every call will receive a reference to the newly transformed value.

The closure can only ever be called once, so think carefully about what transformation you want to apply!

§Panics

This method will panic if the instance has been poisoned during a previous transformation attempt.

The method may panic (or deadlock) upon reentrance.

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pub fn try_get_or_create<F, E>(&self, f: F) -> Result<&U, E>
where T: Clone, F: FnOnce(T) -> Result<U, E>,

Try to get a reference to the transformed value, invoking a fallible f to transform it if the LazyTransform<T, U> has yet to be transformed. It is guaranteed that if multiple calls to get_or_create race, only one will successfully invoke its closure, and every call will receive a reference to the newly transformed value.

The closure can only ever be successfully called once, so think carefully about what transformation you want to apply!

§Errors

Iff f returns a Result::Err, this error is returned verbatim.

§Panics

This method will panic if the instance has been poisoned during a previous transformation attempt.

The method may panic (or deadlock) upon reentrance.

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pub fn get_or_create_or_poison<F, E>(&self, f: F) -> Result<&U, Option<E>>
where F: FnOnce(T) -> Result<U, E>,

Try to get a reference to the transformed value, invoking a fallible f to transform it if the LazyTransform<T, U> has yet to be transformed. It is guaranteed that if multiple calls to get_or_create race, only one will invoke its closure, and every call will receive a reference to the newly transformed value.

The closure can only ever be called once, so think carefully about what transformation you want to apply!

§Errors

Iff this instance is poisoned, except by panics, Err(None) is returned.

Iff f returns a Result::Err, this error is returned wrapped in Some.

§Panics

This method will panic if the instance has been poisoned due to a panic during a previous transformation attempt.

The method may panic (or deadlock) upon reentrance.

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pub fn get(&self) -> Option<&U>

Get a reference to the transformed value, returning Some(&U) if the LazyTransform<T, U> has been transformed or None if it has not. It is guaranteed that if a reference is returned it is to the transformed value inside the the LazyTransform<T>.