Struct Subscription 

pub struct Subscription { /* private fields */ }

One channel subscription on a client. Read what the channel sends with next, watch the connection with next_event, and talk back with perform or send.

Handles are cheap to clone and share one stream of messages: a message goes to whichever handle reads it first. The subscription outlives reconnects, resubscribed automatically, until unsubscribe. Dropping the last handle unsubscribes too, when it happens on a tokio runtime; elsewhere it stops delivery and warns, and the server keeps the subscription until the connection ends.

Implementations

impl Subscription

pub fn key(&self) -> &str

The JSON identifier the server knows this subscription by, and echoes back on everything it sends here.

pub async fn next(&self) -> Option<Message>

The next message the channel broadcast or transmitted, or None once the subscription is unsubscribed, rejected, or the client is closed — err says which. The last callback has returned by then, so a loop that ends knows none is still running or about to.

Read it promptly. A message that arrives with the buffer full is dropped and logged rather than stalling the connection; ClientBuilder::message_buffer sizes the buffer for a slow reader.

pub fn err(&self) -> Option<Error>

Why the subscription ended: Error::Unsubscribed, Error::Rejected, or whatever stopped the client. None while it is live.

pub async fn next_event(&self) -> Option<Event>

The next connection event, in the order they happened, or None once the subscription is over.

A handle keeps the last sixteen events for a reader that isn’t listening, and a reader further behind than that skips the oldest and is told so in the log. Nothing is lost while events are read as they come, and a handle that never reads them costs nothing however long the client runs.

pub async fn perform( &self, action: &str, data: impl Serialize, ) -> Result<(), Error>

Invokes an action on the channel, the equivalent of the JavaScript client’s perform. data must encode to a JSON object, the only shape Rails routes to an action, or to null, which sends the action alone; anything else is Error::DataNotAnObject.

pub async fn send(&self, data: impl Serialize) -> Result<(), Error>

Delivers data to the channel as-is, without naming an action. Rails routes it to the channel’s receive method.

pub async fn unsubscribe(&self) -> Result<(), Error>

Tells the server to drop the subscription and ends both streams. Other subscriptions to the same identifier keep the server’s; it only hears about the unsubscribe from the last of them.

Trait Implementations

impl Clone for Subscription

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Subscription

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

Formats the value using the given formatter.