pub struct ExtensionsMut<'a> { /* private fields */ }
std
only.Expand description
An mutable reference to a Span’s extensions.
Implementations§
Source§impl<'a> ExtensionsMut<'a>
impl<'a> ExtensionsMut<'a>
Sourcepub fn insert<T: Send + Sync + 'static>(&mut self, val: T)
pub fn insert<T: Send + Sync + 'static>(&mut self, val: T)
Insert a type into this Extensions
.
Note that extensions are not subscriber-specific—they are span-specific. This means that other subscribers can access and mutate extensions that a different Subscriber recorded. For example, an application might have a subscriber that records execution timings, alongside a subscriber that reports spans and events to a distributed tracing system that requires timestamps for spans. Ideally, if one subscriber records a timestamp x, the other subscriber should be able to reuse timestamp x.
Therefore, extensions should generally be newtypes, rather than common
types like String
, to avoid accidental
cross-Subscriber
clobbering.
§Panics
If T
is already present in Extensions
, then this method will panic.
Sourcepub fn replace<T: Send + Sync + 'static>(&mut self, val: T) -> Option<T> ⓘ
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.