# Struct once_cell::race::OnceBool

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    pub struct OnceBool { /* private fields */ }

Expand description

A thread-safe cell which can be written to only once.

## Implementations

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### impl OnceBool

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#### pub const fn new() -> OnceBool

Creates a new empty cell.

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#### pub fn get(&self) -> Option<bool>

Gets the underlying value.

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#### pub fn set(&self, value: bool) -> Result<(), ()>

Sets the contents of this cell to `value`.

Returns `Ok(())` if the cell was empty and `Err(())` if it was full.

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#### pub fn get_or_init<F>(&self, f: F) -> bool where
F: FnOnce() -> bool,

Gets the contents of the cell, initializing it with `f` if the cell was empty.

If several threads concurrently run `get_or_init`, more than one `f` can be called. However, all threads will return the same value, produced by some `f`.

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#### pub fn get_or_try_init<F, E>(&self, f: F) -> Result<bool, E> where
F: FnOnce() -> Result<bool, E>,

Gets the contents of the cell, initializing it with `f` if the cell was empty. If the cell was empty and `f` failed, an error is returned.

If several threads concurrently run `get_or_init`, more than one `f` can be called. However, all threads will return the same value, produced by some `f`.

## Trait Implementations

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### impl Debug for OnceBool

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more

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### impl Default for OnceBool

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#### fn default() -> OnceBool

Returns the “default value” for a type. Read more

## Auto Trait Implementations

### impl RefUnwindSafe for OnceBool

### impl Send for OnceBool

### impl Sync for OnceBool

### impl Unpin for OnceBool

### impl UnwindSafe for OnceBool

## Blanket Implementations

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### impl<T> Any for T where
T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more

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### impl<T> Borrow<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

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### impl<T> BorrowMut<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

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### impl<T> From<T> for T

const: unstable · source

#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T where
U: From<T>,

const: unstable · source

#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for T where
U: Into<T>,

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.

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### impl<T, U> TryInto<U> for T where
U: TryFrom<T>,

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.