Struct Snapshot 

pub struct Snapshot { /* private fields */ }

What one request may read: one Arc per section, taken together.

Built by Sections::take when the request begins, and read by an adapter’s extractor. Two reads of the same section answer the same Arc, however far apart in the handler they are and whatever lands in between.

Implementations

impl Snapshot

pub fn get<T>(&self) -> Option<Arc<T>>

where T: Any + Send + Sync,

The section of type T this request began with.

None when T was not among the sections, or was among them and had not loaded yet. require tells those apart.

pub fn require<T>(&self) -> Result<Arc<T>, NotInScope>

where T: Any + Send + Sync,

The section of type T, or why it is not here.

Errors

NotInScope::NotListed when T was never registered — a wiring mistake, fixed where the layer is built. NotInScope::NotLoaded when it was registered and nothing has installed a value yet — a startup-order mistake, fixed by loading before serving. The two have different fixes, which is why they are different variants.

pub fn len(&self) -> usize

How many sections this request may read.

pub fn is_empty(&self) -> bool

Whether it carries nothing at all.

pub fn names(&self) -> Vec<&'static str>

The type names registered, whether or not each had loaded.

pub fn merged_with(self, inner: Snapshot) -> Snapshot

This snapshot with inner’s sections laid over it.

What an adapter uses when layers nest and each carries its own list. The inner one wins where both registered a type, because it is the more specific of the two — and nothing is lost, which is the point: a handler under both layers can read either’s sections.

Trait Implementations

impl Clone for Snapshot

fn clone(&self) -> Snapshot

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Snapshot

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

The section names, never their contents.

A configuration section holds credentials, and {:?} on a request is the kind of thing that reaches a log line.

impl Default for Snapshot

fn default() -> Snapshot

Returns the “default value” for a type.