Trait MessageHeaders 

pub trait MessageHeaders {
    type Contract: HeadersContract;
}

Declares a message type’s typed header contract.

#[derive(Outgoing)] implements it: #[outgoing(headers = Meta)] on the type sets the contract to WithHeaders<Meta>, and a declaration without it sets NoHeaders (#[derive(MessageInfo)] with #[message(headers(Meta))] does the same for a type that declares no destination). The contract types both message documentation (the AsyncAPI headers schema of the message) and the publish builder: publish() compiles only with the headers the contract declares (none for NoHeaders).

The two contract shapes are a closed vocabulary: HeadersContract is sealed.

Examples

use ruststream::prelude::*;

struct ChunkMeta {
    task_id: u64,
}

struct ChunkDone;

// What `#[derive(Outgoing)]` + `#[outgoing(headers = ChunkMeta)]` generates:
impl MessageHeaders for ChunkDone {
    type Contract = WithHeaders<ChunkMeta>;
}

Required Associated Types

type Contract: HeadersContract

The contract shape: NoHeaders, or WithHeaders<H> with the typed header struct H.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl MessageHeaders for String

type Contract = NoHeaders

impl<T> MessageHeaders for Vec<T>

type Contract = NoHeaders

Implementors