Struct Extensions 

pub struct Extensions { /* private fields */ }

A type-keyed map of opaque Arc’d values. Each Rust type T occupies its own slot, so independent components can each attach their own data without conflict.

Cloning is cheap: the backing values are reference-counted.

Example

struct MyData(u32);
struct OtherData(&'static str);

let mut ext = Extensions::new();
ext.insert(MyData(42));
ext.insert_arc(Arc::new(OtherData("hello")));

assert_eq!(ext.get::<MyData>().unwrap().0, 42);
assert_eq!(ext.get::<OtherData>().unwrap().0, "hello");

Implementations

impl Extensions

pub fn new() -> Self

Create an empty map.

pub fn is_empty(&self) -> bool

Returns true if no extensions are set.

pub fn len(&self) -> usize

Number of extensions set.

pub fn insert<T: Any + Send + Sync>(&mut self, value: T) -> Option<Arc<T>>

Insert an extension keyed by its concrete type T. Returns the previous value of that type, if any.

The value is wrapped in an Arc internally. If the caller already has an Arc<T> and wants to avoid an extra allocation, use Self::insert_arc.

pub fn insert_arc<T: Any + Send + Sync>( &mut self, value: Arc<T>, ) -> Option<Arc<T>>

Insert an extension keyed by its concrete type T, taking an already-allocated Arc<T>. Returns the previous value of that type, if any.

pub fn insert_dyn( &mut self, value: Arc<dyn Any + Send + Sync>, ) -> Option<Arc<dyn Any + Send + Sync>>

👎Deprecated since 54.0.0:

use insert or insert_arc; only retained to support the deprecated PartitionedFile::with_extensions shim

Insert an already-type-erased value, keyed by its dynamic TypeId. Used internally to support APIs that accept Arc<dyn Any + Send + Sync> for backwards compatibility and need to recover the concrete type for keying.

New code should use Self::insert or Self::insert_arc, which preserve the concrete type at the call site.

pub fn get<T: Any + Send + Sync>(&self) -> Option<&T>

Borrow the extension of type T, if set.

pub fn get_arc<T: Any + Send + Sync>(&self) -> Option<Arc<T>>

Get a cloned Arc<T> of the extension, if set.

pub fn contains<T: Any + Send + Sync>(&self) -> bool

Returns true if an extension of type T is set.

pub fn merge(&mut self, other: &Extensions)

Merge entries from other into self. Entries in other take precedence over existing entries with the same type.

Trait Implementations

impl Clone for Extensions

fn clone(&self) -> Extensions

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Extensions

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

Formats the value using the given formatter.

impl Default for Extensions

fn default() -> Extensions

Returns the “default value” for a type.