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LiveViewSocket API - Server Events

Server events are important to connect LiveViews with asynchronous processes. For example, a LiveView may need to wait for a long database query or search service to complete before rendering the results. Or a LiveView may want to send updates based on a webhook or action from another user.

LiveViewSocket Properties and Methods

There are two LiveViewSocket API methods that help facilitate server events:

sendInfo(info: Info<TInfos>): void;Send an internal event (a.k.a "Info") to the LiveView's handleInfo method
subscribe(topic: string): Promise<void>;Subscribe to the given topic using pub/sub. Events published to this topic will be delivered to handleInfo.

sendInfo Method

socket.sendInfo enables a LiveView to send message to itself which is useful for executing actions that are asynchronous. Messages sent via socket.sendInfo are received by the handleInfo method after the current render lifecycle has completed. (In other words, handleInfo is called after the render call which will result in another render after handleInfo completes.)

When creating your LiveView you can provide the typing for TInfo which describes the "shape" of the possible info messages. e.g.

// Define the MyContext, MyEvents, and MyInfo types
type MyContext = {query: string, loading: boolean, results: string[]};
type MyEvents = {type: "search", query: string};
type MyInfo = {type: "run_search", query: string} | {type: "refresh"};

// Annotate the createLiveView function with the types
const myLiveView = createLiveView<MyContext, MyEvents, MyInfo>(
handleEvent: (event, socket) => {
if(event.type === "search" ) {
// update the context with loading status and empty results so
// that UI will be updated for user
socket.assign({ loading: true, results: [], query: event.query });
// send internal message to run the search process
socket.sendInfo({ type: "run_search", query: event.query })
handleInfo: (info, socket) => {
if(info.type === "run_search") {
const { query } = info;
// run the search
const results =
// update the context with results which will update the UI
socket.assign({ loading: false, results })

socket.sendInfo can take a type as a string for cases where there isn't additional information passed along with the message.

// or send just the "type" as a string

subscribe Method

socket.subscribe enables a LiveView to subscribe to a topic using pub/sub. Events published to this topic will be delivered to handleInfo. This is useful for cases where a LiveView needs to receive updates from another process or user.

You can provide the type annotation for messages you expect to receive from a pub/sub topic as well.