Struct SseEvent 

pub struct SseEvent { /* private fields */ }

A Server-Sent Event.

Events consist of one or more fields:

• data: The message payload (required, can contain newlines)
• event: The event type (optional, defaults to “message”)
• id: An identifier for the event (optional, used for resumption)
• retry: Reconnection time in milliseconds (optional)
• comment: A comment (not delivered to the event listener)

Example

use fastapi_core::sse::SseEvent;

// Simple message
let event = SseEvent::message("Hello, World!");

// Event with type and ID
let event = SseEvent::new("user joined")
    .event_type("join")
    .id("123");

// JSON data
let event = SseEvent::new(r#"{"user":"alice","action":"login"}"#)
    .event_type("user_event");

// Keep-alive comment
let event = SseEvent::comment("keep-alive");

Implementations

impl SseEvent

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

Create a new SSE event with the given data.

The data can contain newlines - each line will be prefixed with data: .

pub fn message(data: impl Into<String>) -> Self

Create a simple message event.

Equivalent to SseEvent::new(data).

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

Create a keep-alive comment.

Comments are sent but not delivered to event listeners. Use these to prevent connection timeouts.

Example

let keepalive = SseEvent::comment("heartbeat");

pub fn event_type(self, event_type: impl Into<String>) -> Self

Set the event type.

If not set, the event type defaults to “message”.

Example

let event = SseEvent::new("user logged in")
    .event_type("login");

pub fn id(self, id: impl Into<String>) -> Self

Set the event ID.

The client stores this ID and sends it in the Last-Event-ID header when reconnecting, allowing the server to resume from where it left off.

Example

let event = SseEvent::new("data")
    .id("12345");

pub fn retry_ms(self, milliseconds: u64) -> Self

Set the retry timeout in milliseconds.

This tells the client how long to wait before attempting to reconnect if the connection is lost.

Example

let event = SseEvent::new("data")
    .retry_ms(5000); // 5 seconds

pub fn retry(self, duration: Duration) -> Self

Set the retry timeout from a Duration.

Example

use std::time::Duration;

let event = SseEvent::new("data")
    .retry(Duration::from_secs(5));

pub fn to_bytes(&self) -> Vec<u8>

Format the event as SSE wire format.

Returns bytes ready to be sent to the client.

Trait Implementations

impl Clone for SseEvent

fn clone(&self) -> SseEvent

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SseEvent

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

Formats the value using the given formatter.

impl From<&str> for SseEvent

fn from(data: &str) -> Self

Converts to this type from the input type.

impl From<String> for SseEvent

fn from(data: String) -> Self

Converts to this type from the input type.