Struct SynchronizedOptional 

pub struct SynchronizedOptional<T> { /* private fields */ }

Available on crate feature std only.

Basically a RwLock<Option<Arc<T>>> - the benefits here being:

1. This structure is Sync in that it can be shared between threads
2. This structure can be lazily initialized, and then reset back to None, and back again
3. This structure provides multiple access to a single shared instance, like a String so we’re not cloning it a bunch of times unnecessarily. (Arc<T>)

The Arc<T> bit is because you can’t return a &T out of a RwLock<T> the way you can from a std::sync::OnceLock<T>. The only reason this isn’t a OnceLock is because I wanted a swap method that was atomic, rather than relying on a std::sync::OnceLock<T>::take followed by a std::sync::OnceLock<T>::set, which allows a very slight race condition.

Implementations

impl<T> SynchronizedOptional<T>

pub fn empty() -> Self

Returns a new uninitialized/empty struct

pub fn new(value: T) -> Self

Returns a new struct initialized with the provided value

pub fn new_shared(value: Arc<T>) -> Self

Returns a new struct initialized with the provided already shared value

pub fn get(&self) -> Option<Arc<T>>

If this struct has been initialized, returns a copy of the data, otherwise None

pub fn set(&self, value: Option<T>) -> Result<(), Option<T>>

Sets the value to be the specified value, throwing away any value that was stored previously Returns the value provided as a parameter if it was unable to replace the value.

pub fn set_shared(&self, value: Arc<T>) -> Result<(), Arc<T>>

Sets the value to be the specified value, throwing away any value that was stored previously Returns the value provided as a parameter if it was unable to replace the value.

pub fn take(&self) -> Option<Arc<T>>

Takes the value out of this structure, leaving None in it’s place.

pub fn swap(&self, value: T) -> Result<Option<Arc<T>>, T>

Swaps the value contained within this structure (if any) with the value provided. Upon success, returns the old value (which is possibly None). Will only fail if the lock has been poisoned, at which point it returns the provided value back to you.

pub fn swap_shared(&self, value: Arc<T>) -> Result<Option<Arc<T>>, Arc<T>>

Swaps the value contained within this structure (if any) with the already shared value provided. Upon success, returns the old value (which is possibly None). Will only fail if the lock has been poisoned, at which point it returns the provided value back to you.

Trait Implementations

impl<T> Debug for SynchronizedOptional<T>

where T: Debug,

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

Formats the value using the given formatter.

impl<T> Default for SynchronizedOptional<T>

fn default() -> Self

Returns the “default value” for a type.