Struct ExtensionsMut

pub struct ExtensionsMut<'a> { /* private fields */ }

Available on crate feature std only.

An mutable reference to a Span’s extensions.

Implementations

impl<'a> ExtensionsMut<'a>

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

Insert a type into this Extensions.

Note that extensions are not Layer-specific—they are span-specific. This means that other layers can access and mutate extensions that a different Layer recorded. For example, an application might have a layer that records execution timings, alongside a layer that reports spans and events to a distributed tracing system that requires timestamps for spans. Ideally, if one layer records a timestamp x, the other layer should be able to reuse timestamp x.

Therefore, extensions should generally be newtypes, rather than common types like String, to avoid accidental cross-Layer clobbering.

Panics

If T is already present in Extensions, then this method will panic.

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

Replaces an existing T into this extensions.

If T is not present, Option::None will be returned.

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

Get a mutable reference to a type previously inserted on this ExtensionsMut.

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

Remove a type from this Extensions.

If a extension of this type existed, it will be returned.

Trait Implementations

impl<'a> Debug for ExtensionsMut<'a>

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

Formats the value using the given formatter.