Struct Config 

pub struct Config<T>(pub Arc<T>);

One section of this request’s configuration.

async fn handler(Config(db): Config<Database>) -> String {
    db.host.clone()
}

Extracting the same type twice in one handler answers the same Arc. Extracting one the layer was not given is a wiring mistake and answers 500 — see SnapshotMissing.

Tuple Fields

0: Arc<T>

Trait Implementations

impl<T> Clone for Config<T>

fn clone(&self) -> Self

Hand-written: cloning an Arc never needs T: Clone, and a derive would demand it of every section.

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

Performs copy-assignment from source.

impl<T> Debug for Config<T>

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

The type’s name, never the section’s contents.

A configuration section holds credentials, and ?config in a tracing call is exactly how one reaches a log line. Snapshot holds the same line; this is the extractor keeping it.

impl<T> Deref for Config<T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<S, T> FromRequestParts<S> for Config<T>

where S: Send + Sync, T: Any + Send + Sync,

type Rejection = SnapshotMissing

If the extractor fails it’ll use this “rejection” type. A rejection is a kind of error that can be converted into a response.

async fn from_request_parts( parts: &mut Parts, _state: &S, ) -> Result<Self, Self::Rejection>

Perform the extraction.