Struct Channel 

pub struct Channel<T> { /* private fields */ }

Defines one durable FIFO queue of typed messages.

Add the Channel to crate::PersistenceSchema. Clients and handlers may publish messages; Steps create Condition values that wait for queue-size bounds and read the messages consumed by the satisfied condition.

Handler publications and deletions are staged until successful return. A satisfied wait consumes messages before Execute; it does not combine that consumption with later publications into one transaction. Pending-message reads are snapshots that other handlers can change. Select pending-message loads explicitly. Use transactional RPC execution for atomic deletion and publication, and a shared Attribute lock when all cooperating writers must serialize a decision about the queue. T must implement Value when publishing or reading messages. Declare reusable definitions as module-level std::sync::LazyLock statics.

Examples

use dex_sdk::{Channel, Wait};

let approvals = Channel::<String>::new("approvals");
let wait = Wait::until(approvals.for_one());

Implementations

impl<T> Channel<T>

pub fn new(name: impl Into<String>) -> Self

Defines a Channel with a stable name.

Slash is prohibited because it is a reserved character.

pub fn publish(&self, context: &mut Context, value: T) -> HandlerResult<()>

where T: Value,

Stages one message from the current Step or RPC invocation.

Errors

Returns a crate::HandlerError when value cannot be encoded.

pub fn delete( &self, context: &mut Context, message_id: &str, ) -> HandlerResult<()>

Stages best-effort deletion of one pending message from a handler.

pub fn size(&self, context: &Context) -> HandlerResult<usize>

Returns the invocation snapshot’s queued-message count.

pub fn pending_messages( &self, context: &Context, ) -> HandlerResult<Vec<ChannelMessage<T>>>

where T: Value,

Returns loaded pending messages from the invocation snapshot in FIFO order.

Errors

Returns a crate::HandlerError when this Channel was not selected by the handler options or when decoding fails.

pub fn find_pending_message( &self, context: &Context, message_id: &str, ) -> HandlerResult<Option<ChannelMessage<T>>>

where T: Value,

Finds one pending message by its Dex-assigned ID.

Returns Ok(None) when the loaded snapshot does not contain message_id.

Errors

Returns the same errors as Self::pending_messages.

pub fn condition_results(&self, context: &Context) -> HandlerResult<Vec<T>>

where T: Value,

Decodes messages consumed by this Channel’s satisfied condition.

Errors

Returns a crate::HandlerError when a message cannot be decoded.

pub fn for_one(&self) -> Condition

Creates a condition that consumes exactly one queued message.

pub fn for_n(&self, count: usize) -> Condition

Creates a condition that consumes exactly count queued messages.

pub fn at_least(&self, count: usize) -> Condition

Creates a condition satisfied when at least count messages are queued.

pub fn at_most(&self, count: usize) -> Condition

Creates a non-blocking condition consuming up to count queued messages.

When its surrounding Wait completes, it consumes messages queued then. An empty queue yields no messages.

pub fn range( &self, at_least: Option<usize>, at_most: Option<usize>, ) -> Condition

Creates a condition that waits for the lower bound, then consumes up to the upper bound.

Omitting the lower bound makes the condition complete immediately. Consumption uses only messages queued when the condition completes.

pub fn when_empty(&self) -> ChannelGuard

Creates a guard used by conditional Flow completion to require an empty queue.

Trait Implementations

impl<T> Clone for Channel<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.