Use

The best way to use data/worker is to create a connection module that works when loaded in either the window or in a Worker. This pattern tends to work even if workers are not supported.

The following creates a connection that does the work of cache-requests, data/url, and memory-cache in a worker thread.

The todo_connection module can be found here and looks like the following:

import connect from "can-connect";
import fixture from "can-fixture";

// If we are in the main thread, see if we can load this same
// connection in a worker thread.
let worker;
if ( typeof document !== "undefined" ) {
    worker = new Worker( System.stealURL + "?main=can-connect/data/worker/demo/todo_connection" );
}


// create cache connection
const cache = connect( [
    require( "can-connect/data/memory-cache/" )
], {
    name: "todos"
} );

// Create the main connection with everything you need.  If there is a worker,
// all data interface methods will be sent to the worker.
const todosConnection = connect( [
    require( "can-connect/data/url/url" ),
    require( "can-connect/cache-requests/cache-requests" ),
    require( "can-connect/data/worker/worker" ),
    require( "can-connect/constructor/constructor" ),
    require( "can-connect/constructor/store/store" )
], {
    url: "/todos",
    cacheConnection: cache,
    worker: worker,
    name: "todos"
} );


fixture.delay = 1000;
fixture( {
    "GET /todos": function( request ) {
        return { data: [
            { id: 1, name: "wash dishes" },
            { id: 2, name: "mow lawn" },
            { id: 3, name: "do laundry" }
        ] };
    }
} );

export default todosConnection;

The things to notice:

1. A Worker should be passed as the worker option that loads a connection with the same name as the connection in the window. In thise case, the same connection module is loaded so everything works.

2. A single Worker could load multiple connection modules and perform other behaviors.

Split Connection Logic

THe previous example used a single module that was loaded by both the window and the worker. This doesn't have to be the case. Two different modules could be used. For example, todo-window.js and todo-worker.js. Each might look like:

// todo-window.js
const workerURL = System.stealURL + "?main=app/models/todo-worker";

const todoConnection = connect( [
    require( "can-connect/data/worker/worker" ),
    require( "can-connect/constructor/constructor" ),
    require( "can-connect/constructor/store/store" )
], {
    worker: new Worker( workerURL ),
    name: "todos"
} );

// todo-worker.js
const cache = connect( [
    require( "can-connect/data/memory-cache/memory-cache" )
], {
    name: "todos-cache"
} );

const todoConnection = connect( [
    require( "can-connect/data/url/url" ),
    require( "can-connect/cache-requests/cache-requests" ),
    require( "can-connect/data/worker/worker" )
], {
    url: "/todos",
    cacheConnection: cache,
    name: "todos"
} );

However, the problem with the two-module approach is that it will not work if Workers are not supported by your browser.