Struct zng_app_context::AppLocal

pub struct AppLocal<T: Send + Sync + 'static> { /* private fields */ }

An app local storage.

This is similar to std::thread::LocalKey, but works across all threads of the app.

Use the app_local! macro to declare a static variable in the same style as thread_local!.

Note that in "multi_app" builds the app local can only be used if an app is running in the thread, if no app is running read and write will panic.

Implementations

impl<T: Send + Sync + 'static> AppLocal<T>

pub fn read(&'static self) -> MappedRwLockReadGuard<'_, T>

Read lock the value associated with the current app.

Initializes the default value for the app if this is the first value access.

Panics

Panics if no app is running in "multi_app" builds.

pub fn try_read(&'static self) -> Option<MappedRwLockReadGuard<'_, T>>

Try read lock the value associated with the current app.

Initializes the default value for the app if this is the first value access.

Returns None if can’t acquire a read lock.

Panics

Panics if no app is running in "multi_app" builds.

pub fn write(&'static self) -> MappedRwLockWriteGuard<'_, T>

Write lock the value associated with the current app.

Initializes the default value for the app if this is the first value access.

Panics

Panics if no app is running in "multi_app" builds.

pub fn try_write(&'static self) -> Option<MappedRwLockWriteGuard<'_, T>>

Try to write lock the value associated with the current app.

Initializes the default value for the app if this is the first value access.

Returns None if can’t acquire a write lock.

Panics

Panics if no app is running in "multi_app" builds.

pub fn get(&'static self) -> T

where T: Clone,

Get a clone of the value.

pub fn set(&'static self, value: T)

Set the value.

pub fn try_get(&'static self) -> Option<T>

where T: Clone,

Try to get a clone of the value.

Returns None if can’t acquire a read lock.

pub fn try_set(&'static self, value: T) -> Result<(), T>

Try to set the value.

Returns Err(value) if can’t acquire a write lock.

pub fn read_map<O>( &'static self, map: impl FnOnce(&T) -> &O ) -> MappedRwLockReadGuard<'_, O>

Create a read lock and map it to a sub-value.

pub fn try_read_map<O>( &'static self, map: impl FnOnce(&T) -> &O ) -> Option<MappedRwLockReadGuard<'_, O>>

Try to create a read lock and map it to a sub-value.

pub fn write_map<O>( &'static self, map: impl FnOnce(&mut T) -> &mut O ) -> MappedRwLockWriteGuard<'_, O>

Create a write lock and map it to a sub-value.

pub fn try_write_map<O>( &'static self, map: impl FnOnce(&mut T) -> &mut O ) -> Option<MappedRwLockWriteGuard<'_, O>>

Try to create a write lock and map it to a sub-value.

pub fn id(&'static self) -> AppLocalId

Gets an ID for this local instance that is valid for the lifetime of the process.

Note that comparing two &'static LOCAL pointers is incorrect, because in "hot_reload" builds the statics can be different and still represent the same app local. This ID identifies the actual inner pointer.

Trait Implementations

impl<T: Send + Sync + 'static> PartialEq for AppLocal<T>

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: Send + Sync + 'static> Eq for AppLocal<T>