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.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 16 bytes