Struct Extensions 

pub struct Extensions { /* private fields */ }

A map from a type to one value of that type.

Only one value per type can be stored; inserting again replaces it. Wrap in a newtype when you need two values of the same underlying type with different meanings (e.g. struct RequestId(String) vs struct TraceId(String)).

Implementations

impl Extensions

pub fn new() -> Self

An empty bag.

pub fn insert<T: Send + Sync + 'static>(&mut self, value: T) -> Option<T>

Store value, returning whatever value of the same type it replaced.

pub fn get<T: Send + Sync + 'static>(&self) -> Option<&T>

Borrow the stored T, if there is one.

pub fn get_mut<T: Send + Sync + 'static>(&mut self) -> Option<&mut T>

Mutably borrow the stored T, if there is one.

pub fn remove<T: Send + Sync + 'static>(&mut self) -> Option<T>

Remove and return the stored T.

pub fn contains<T: Send + Sync + 'static>(&self) -> bool

Whether a value of type T is present.

pub fn get_or_insert_with<T: Send + Sync + 'static>( &mut self, default: impl FnOnce() -> T, ) -> &mut T

Borrow the stored T, inserting the value from default first if it is missing.

pub fn len(&self) -> usize

How many values are stored.

pub fn is_empty(&self) -> bool

Whether the bag holds nothing.

pub fn clear(&mut self)

Drop everything.

Trait Implementations

impl Debug for Extensions

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

Formats the value using the given formatter.

impl Default for Extensions

fn default() -> Self

Returns the “default value” for a type.